Wow. That is wild. Some thoughts:
1. Okay, first of all, which SNL writer is One of Us?
2. It strikes me that she is not very ticklish at all, at least in the areas they're tickling her. Granted, their technique is terrible (whether that's intentional so as to make it more tolerable, or they're just genuinely bad ticklers is up for debate), but a lot of people in that position would never be able to hold as still as she does, in both of the tickling scenes. Most people would at least be squirming a fair amount, and a lot would be laughing their heads off.
3. In a way, though, her lack of ticklishness opens the door for us to consider a lot of what might have happened behind the scenes. It makes me wonder what kind of conversations among the writers and cast might've gone on about her ticklishness and the tolerability of their attacks. Did Heidi Gardner, Ego Nwodim, or Cecily Strong utter things like "I would never be able to get through this" or "I have no idea how you can handle that!" (or at least think it)? How many viewers at home commented similarly or at least had those thoughts while imagining themselves in that position?
4. Along those lines, it also makes me wonder if the writers had pitched that skit to other hosts, only to have them turn it down because they knew they'd be too ticklish to handle it. It's totally conceivable they pitched it to Billie Eilish, Zoe Kravitz, or Selena Gomez earlier this season—or even a musical guest like Taylor Swift. I know that might be a stretch, but if you were a ticklephile who had a job as a writer on SNL and had been bold enough to write and pitch this sketch, wouldn't you have tried to go for the gold and propose it to Taylor, if only just to see what she'd say?