That's a good answer, not everything is all theory and research, it takes experience with real people over time to be good at coaching or rehab - a health professional has told me exactly that and you have been doing that. I assume that you are doing real in person coaching and not online stuff? Its very easy for a novice to get carried away with weight lifting and get hurt, I don't think it is suited to online coaching or for those who want to push their limits. I would imagine you would need to see for yourself how your student is moving and how much they are exerting themselves. The more gentle stuff such as GMB is more suited to online.Maybe you should stop guessing?
Its going to be different for everyone. I've arrived at squatting 275# for a set of five as my arbitrary number because the demographic I work with responds well when they reach that point and after that there are diminishing returns and we begin to move into the personal preference range, be it feeling, athletic performance etc etc. There are some lifters who due to genetics and or age will never reach that goal because they started much to late in life or for any number of reasons do not have the capacity to reach that goal. For them, training continues as a part of living a healthy full life.
Instead of twisting things and focusing on doing the absolute bare minimum you could look at the in a very simple and logical way. We know injuries are going to happen at some point. Would you rather be 1. injured and weak, or 2. injured and strong.
Your point on better to be injured while strong - I have had shoulder surgery - about 20 yrs ago I wish to point out! Anyway there was a bit of a wait for the op and the physio put me on a shoulder strength program in preparation. I questioned that wouldn't it be more important after the op than before - the explanation was that I would bounce back much faster with the post op rehab if I went into it strong.
I have no argument with your suggestion that maybe I should stop guessing. Ideally I would be looking at a personal coach to take some of the guesswork out. The reality is there would be an opportunity cost. To stay in a reasonable budget I would be looking at discontinuing my long term maintenance program, which is chiro adjustment and massage every 3 weeks. I consider myself to be in a fairly good place coz the chiro lifts weights and I therefore have easy access to information and advice specific to me. I'm also getting feedback from the massage therapist who can spot things going on such as things tightening up. I've already given the example of the back hyper extension which I have corrected and might have caused me problems down the track if I hadn't. Also the piriformis tightness which I would not know about.
The personal trainer would cost and I would need gym membership. Unlike the chiro and massage I won't recover any of the cost from my health insurance.
I won't rule out a personal coach in the future, its going to take a life changing event for me to do that, but they happen. Maybe you should consider trying a deep tissue massage as part of your post workout recovery. I guarantee the therapist would find muscle knots and tightness that you are not aware you have. Whether relieving it with manipulation is helpful I know is a matter that we have debated. However not everything in coaching and rehab has been proven with research papers - some of it comes down to experience and perception. A bit like that 275 number you have come up with, although I concede that weight training is one of the more clear cut things to monitor.