Does squatting heavy really improve your upper body strength?

I've been lifting using SL5x5 since about a year ago. I'm currently lifting:

Bench: 70kg Squat: 100kg Deadlift:120kg Barbell Row: 50kg (I realized I was doing pendlay rows, so I de-loaded and restarted) OHP: 50 kg

BodyWeight: 82kg Body fat (Calipers): 17%

As you can see, I seem to be turning into a t-rex.

Strong lifts heavily emphasizes the squat. The program's website states that improvements in the squat will improve overall strength.

But somehow my bench and OHP have stalled while my squat has kept increasing. Should I take it easy with squats while doing supplementary exercises so my upper body lifts can catch up?