Honestly, I would take butts just being more nicely shaped, we know it's possible, the sheer popularity of 2B's panties over any of the dozens of others skimpy bottom pieces owes itself to the fact it gives your character a much nicer rear, and while I understand that this is to make the cosplay set more accurate to how 2B looks, the boots do something similar to your legs to much less... satisfactory degree, I also frankly haven't a clue why that didn't become the standard after the Nier raids, it was clearly popular, but even recent sets still have the much flatter butt.