Split 9s vs 7?

So I'm always told splitting 9s against a dealer 7 is just "basic strategy" but lately I've been getting this itch that maybe it's a spot that's a little more nuanced. Like, 9 and 9 gives you 18, which isn't terrible against a 7 upcard - dealer probably lands on 17 or 18 pretty often anyway. But every chart just shoves "split" down your throat, no exceptions.

I know splitting ups your chance at two decent hands instead of settling for one strong-but-not-great one. But has anyone run the math for short decks or shoes under six decks, or different rulesets like no double after split? Does the logic still totally hold up, or is there actually an argument for standing sometimes?