Compounds - using more/bigger muscles - generate more test/HGH, IIRC, leaving a better environment for tiny muscles in isolation.
Practically, fatigue is the only real determinant of workout structure...
Not strictly true, but yeah, compounds tend to cover the bigger muscle groups. And working legs/back etc tend to trigger the body to release more testosterone, although I'm not sure HGH is affected in the same way?
I'm never going to lift epic weights with squats, I've accepted that now, so I tend to rely on pre-exhaustion to stimulate growth. And I guarantee doing those squats last was harder than me doing 120-130kg working sets first
