If I may offer my limited experience with squatting there are a few things I’ve noted
1.) Most people have tight soleus or hip flexors which often affects there squatting.. while people do a lot of standing stretches for calf’s there’s often not many done with a bent knee.
2.) Without getting into a flame war, In reply to andrews post about so many injuries in league… I think its fair to say that because of the nature of the sport you’d be extremely lucky to get through a year without an injury… Form goes out the window with the forces involved in contact sports so while it maybe true that certain people are lacking thoracic mobility or whatever I don’t think you can attribute that to the high injury rate.
3.) I think you could debate powerlifting depth VS olympic depth all day but I think they’re both valid and I’d think it would depend on the individual and there build/injury history. Also the difference between winning and losing on the field isn’t going to be whether a player has squatting to 90degrees or 110 degrees its going to be how he converts the in gym performance to the field.
As I tell the guys I work with ‘A gain of 5kgs on your squat isn’t going to make you a better player BUT training to get that gain will’
Hope my minor contribution can help in some way