Yeah, the point is that everyone benches more in the rack because you don't lose anything to lateral movement ("balancing the weight.") Since the bar is locked in, your max on the machine will be somewhere between the "max" of your stronger side and the "max" of your weaker side. If you have a free bar, then you're limited by what your weaker side can accomplish, plus the challenge of restricting lateral movement.

I mean, Jesus Christ, who doesn't intuitively know this?