What gave Lyle away is his questioning of the young fella's squats. Going from squatting 80kgx5 to squatting 150kg 5RM at 110kg BW after 6 months of serious linear progression training under a good coach is nothing extraordinary, it's just about right.
As I have
previously mentioned, such results are indeed extraordinary, that is, the ordinary trainee doesn't achieve them - so much so that if they do, people either claim fraud or drug use.
This is simply because most people, even those with trainers, are not engaged in progressive resistance training. That is, they chop and change their exercises all the time so can't progress on them, or else if they do the same exercises, they do the same weight, sets and reps, or at best they push themselves on 1 or 2 favourite exercises like bench and curl, and slack off on the rest.
Since most people in gyms are not engaged in progressive resistance training, they don't get the benefits of progressive resistance training. So when people look around gyms, they figure that lifting weights is useless, and they get warped ideas of what's possible.
Like the trainer who accused my client of using steroids, when Lyle says Zach's results are impossible, what he's really saying is, "when I train people, they never get results like that." He's admitting that he's a crap trainer.