I would venture to guess that you average redditor is not terribly familiar with how wood works.

Very cool, but I’m curious. Why are those last few cuts needed? Are they just done to make this unexpected?!

I was expecting some kind of horrible accident

Well if you break both arms, she's going to help you any way she can...

Only unexpected if you're not familiar with how wood works.

I am guessing that as the extra cuts are for expansion from the smaller bits compressing and therefore expanding slightly.

Just a guess though

Venturing into some questionable territory here.

Joiner biscuits are added and glued in those spots to strengthen the corner.