Just a point on machines (leg press). The force on the feet for the leg press can be far more than what can be on a squat.
The exercise is, while close, of course different than a squat.,
A partial press of 1,000lbs on a 45degree press is roughly 600-700lbs on the feet.
Compare that to what the same person could do (300lbs + 140lbs body = 440lbs) on the squat rack.
It primarily focuses on the same muscles used for power on the bike, while squats are much more of a whole body workout.