Please explain, thank you.

Blame random number generators. Also, in East Asian Countries, the symbol is used for divinity and spirituality. It's not going to be changed.

Looks like a pinwheel shape to me, they're pretty common.

TA maps are static, and it is in fact a swastika. I feel like it's kinda common knowledge now, but the reason it's there is because a lot of Asian cultures have a significantly different meaning tied to the symbol than we do here in the west.

Given the nature of TAs it'd probably be fairly difficult to change the shape of the map while also keeping it consistant in how long it takes to get through.

Won't it provide some legal problems though?

No. It's pretty distinct from the nazi symbol (opposite direction, not on an angle, for a start) and plenty of games have used it for map layout over the years.