I don't view "parlor tricks" as being entirely negative. They're quick, showy demonstrations of skills that are clearly unusual. As long as they are in fact showing the interesting skill--having a dozen people push on you isn't quite as hard as it looks, but does demonstrate that you're hard to push over. If all they're doing is demonstrating that you've trained your ukes to fall over when you look at them, they become less interesting.
I don't disagree with that point, as long as the "parlor tricks" with multiple ukes are for show, not teaching.
Adding ukes where one will suffice to teach a particular body skill, is an embellishment that distracts from the core practice. I'm pretty sure that the kungfu troupe didn't train their individual skills by having 20 guys push on them. They just did a lot of solo and paired practice.