I would say the athlete 9 out of ten times cause 9 out of ten times they lie to the coach and the coach is not always there to babysit them. This is not rocket science.
The answer really is in what is the coach's track record, so if the coach has brought overall trophies to his athletes then some athlete claims he look like shit cause of him then that athlete is just a lazy loser who could not follow directions because of lack of will.
If the coach has a rep to not have any of his athlete place then why is the athlete going with him in the first place, so for sure 9 out ten times the athlete
Some coaches though have very simplistic approach.
If it does not work up the dose and lower the calories and up the cardio. Does it work? Yes, for most. Sometimes though when you lower calories everything that happens is muscle loss and not the shredded glutes you wanted. We both know that getting to around 8% is simply a matter of calories in and out and some test. But at higher level it takes more that that for some.
Then people sometimes fuck themselves up with too much drugs, especially t3.
Then there is this coach in PL that takes cares only of people he knows may be champions. It isn't really hard to tell. He doesn't give a flying fuck about the rest, they're only for money. He didn't answer calls from competitors DURING competition more than several times.
I would NEVER hire a coach. I mean please, every coach I know talks about importance of GI, how simple carbs are bad, how important it is to eat many meals to "strike the metabolic fire" and so on...