I did wonder if that one provocative statement would even be noticed :-)

You make a good argument. I see the functional point of a top cut. Helps prevent condiment excursions. Less likely to break in half. BUT, it's just so much bread. And the hotdog does want to pop out.

I'm unaware of any baseball park or hotdog stand where top-cut buns are sold. This is clearly an established best practice. Hotdog consumers have made an aesthetic choice here.