First off, POTA is not a contest. It’s an ongoing activity … no start or end dates, no required exchange, no score keeping, no competition unless one chooses (I compete only with myself). So spotting is not only allowed, but encouraged.
SKCC is another group that has an excellent spotting page (one of best). It’s called the “sked page”. But during contest activities the use of the sked page is disallowed for contest participants.
WWFF is a lot like POTA, and spotting on their site lets the world know I’m on the air at some reference, and the DX comes rolling in. Again, not a contest.