Not currently. The implication is that the person is in the middle of their turn, and needs to choose between the two letters, but that means that SA was already played in a previous turn, and while I'm unsure if SA is a proper two letter word in any language, I am sure SA isn't a proper two letter word in English because my family had the list of two and three letter words in the official Scrabble dictionary, and SA isn't on the list. Sh, si, so, and st, are.

Isn't AS a word, and so is PI...or can't words go up instead of down? I don't play Scrabble and have only typical knowledge of it.

That's my favorite challenge bait tactic. If you challenge an opponent's word and you're wrong, you lose your turn, so if you want to be an asshole, play a word that exists as an obscure but valid word, but is much more well known as a proper name. Mike (alternate spelling of mic), Jenny (female donkey), Japan (a type of varnish), etc. They challenge, it's in the dictionary, you get to give the opponent a smug grin, and they probably won't want to play Scrabble with you anymore but you just got a major advantage.

If they get used to your tricks, just bullshit them with names that they "know better than to challenge now". It's entirely legal to intentionally play fake words, they're just vulnerable to being challenged.

Of course if you're playing against someone who's actually competitive at Scrabble they've probably dedicated time to studying challenge bait and would see right through you, it's a legit part of the game at a high level so they'd be prepared.

The shorthand to avoid writing sexual assault isn't an actual word.