I have a theory about this - tldr: it's from advice from Quickshot
QS had that mental health break the other year, and when he came back he was v heavy on the costumes and crazy hair cuts. I suspect that dressing up helped him feel more confident since he was 'playing another character'
Now that Ender didn't have a great year in NA I suspect the costumes are serving a similar puprose.
Might be wrong but this my read lol