This is an issue from ChessUp 1, batch 1 in 2022. This is not valid for ChessUp 2 pieces.
We cannot fully scrub the internet of the advice, but just noting it here. ChessUp 2 pieces do not benefit from poking a hole.
This was an issue in ChessUp 1 with trapped air and the felt would form a bulge at high elevations. It was in essence piercing a balloon to fix.