In any sort of production business, efficiency is king. They could change the mockup if they wanted to, but they didn't. They just hid the boxes that weren't relevant. Which, again, is proven by the space for Ken being included in the design. It's just the easiest way to go about doing it, regardless of potential spoilers. Launching a game like this is a huge effort involving every aspect of the company, little things like this slip through sometimes.
I think that's the main point that a lot of people aren't getting. Any argument against the box theory that I've seen are all easily refuted by the fact that a spot of Ken was included on the box.
Yes, they could just resize the boxes. But they didn't. They included a spot for everybody and put everybody in their spot, then just hid the characters that hadn't been revealed.