Penny, this is hard for me to answer. Before I get really longwinded, I'd better point out that my recent experience does not cover high volumes. About 25% of my reps have a higher volume at maybe 50 or 60 calls per day (that used to be 100 or more, before I came abord and contributed to some changes that brought the calls down). What I concentrate on is not high volume on a single area, but contact and administrative operations for multiple clients (instead of dozens of calls per day for one person, maybe dozens of clients per year). So I have to put myself in your shoes and try to use some good thinking about the situation.
I wonder if it is acceptable to abbreviate what is stated on laws, procedures, so that you save time in order to tackle issues. I'm not talking about skipping information, I am asking whether this is a script you must follow or whether you can use your own words? Chances are there is not a lot of room to translate verbiage into other words where you work. Do you know through reports that were shared to the team that it takes 2 minutes go through the preamble stuff (privacy, etc)? Or is this your best hunch? Do you know what your average is? What your shortest time and longest times are, and what times of the day?
There is hope for you to come to a point where you understand how to make the majority of your calls closer to 5 minutes. What I gather from you is that you are enthusiastic about this position. Keep in mind, I am not perfect and my computer screen is not a crystal ball, but I sense that you derive pleasure from talking and going through all the fine details there are to a job. This tells me that your instinct is to be on the side of making extra doors available to callers as opposed to racing through a conversation with doorways to other topics kept shut. There's a balance to find. You ought to be able to find it (in no certain order) through coworkers (maybe on lunch you would hear ideas); through other roles in the department (is there a "coach" who monitors calls, maybe someone other than the supervisor?); through your supervisor; and through your own experience. You will recognize how to handle the calls more smoothly and how to react to problems more readily as time goes on. Part of understanding the balance would be realizing that you want to make a conversation meaningful for one particular customer, but that you also have to conduct a successful conversation with several other customers (not one but many people have to count). Finding a way to achieve both of those things (meaningful conversations--but one person at a time) is more of an art than a science, I guess, and saying that you need to handle 80 calls at 5 in on average is the language of science. Try to dabble in both art and science and see what you can do.
Now to talk about my computer screen that is not a crystal ball again. I can't tell what took place in that conversation with your supervisor; all I can do is take a look at the words you put down. One of my first thoughts was to disagree with saying "Maybe this job is not for you?" as a response. That has a ring to it that shows the supervisor didn't have time for the question--or wanting to close off the questions raised. I think it's important to understand that supervisors are not perfect and will not use the best reactions all of the time. I think this was one of his bad days, but let's use some optimistic thinking now that I've said that.
On the other hand, was there anything that would have led him to react this way, was he reading "defeatism" in your words or your body language? A good reason for thinking about that is that he might not understand the positive energy you have to bring to the work. He could have heard a similar question from others dozens of times (even before the new training initiative intended to provide one-stop info), and assumed you were not interested in "trying" to achieve the goal. I'm not sure how observant your supervisor is, but I think the sharpest supervisors know which signs are the ones to watch for. Sometimes questions surrounding "change" and "new procedures" and "how is this possible?" raise flags for supervisors, correctly or incorrectly. This is because they become accustomed to recognizing the slightest sign of resistance and have to prepare for the potential to bring in new staff.
I may not have been smart enough at that moment to say this, and I may not even have been empowered to do this at your company, but my my reaction would have challenged you at what you actually know about the lengths of time A, B or C take on a call; and to ask you where you think you would find the hardest time wading through the heavy waters fast enough...and find a way for you to speed that up or think up some other kind of plan. And I would watch for the willingness to think through the mud until you found fresher water. That would have allowed for some two-way street. It's a fact that you have to make concessions as a CSR handling calls, and you shouldn't expect that you necessarily know that a goal is doomed--or allow anyone to interpret that thinking in you.
If you think there is any possibility that you are not being interpreted as an interested employee, I think you should make a deliberate effort to use language that shows your "interest in meeting requirements"; "how you can create efficiency during your calls"; "how you can cover policy details yet respond to needs." I think you are probably doing that already (if you're spending time discussing topics here), but there could be room to more specific about it at the right times.
Outside of all that...there is also the possibility the company has not thought of everything. Maybe they will discover that the required metrics are not suitable. Maybe you will be right, and maybe more than one person shares your concerns. But we're just not there yet. The way I would go is to see what I could do. I'd remind myself I can handle more than one thing at once and be openminded about how to get there.
Will watch to see how this goes.