Yes, uniformity is the goal. There is a technique, and the members are instructed to adhere to it. So what is the difference between marching technique and emotional performance technique?

Marching technique - say the goal is to get your legs as straight as possible. Some will achieve better than others, but the point is that everyone on the field is doing their best to achieve straight legs. If everyone didn't have the mindset of being the best individual, then uniformity would be out the window. Everyone strives to have the straightest legs, and from the outside it looks uniform.

Emotional performance technique - say the goal is to emote triumph. Some will achieve better than others, but the point is that everyone on the field is doing their best to portray the emotion of success and grandeur. If everyone didn't have the mindset of portraying the emotion the biggest and most clearly, then the uniformity would be out the window. Everyone tries to portray the emotion, and from the outside it looks uniform.

And for what it's worth, I haven't downvoted you at all. Those are the people observing our exchange.