PRS' service bot intercepted my email, and gave me a couple of articles to choose from. If they answered my question, I could close my request. Here's the helpful one:
What type of finish does PRS use on CORE guitars?
From 1985 – 2019, PRS used a polyester basecoat and an acrylic topcoat. During 2019, we started to transition to a nitrocellulose over CAB (catalyzed acrylic) finish. This was a flying change that was slowly worked into production. If your guitar was made during 2019, we cannot accurately determine the exact finish used on your instrument, so it is best to treat it as you would any other nitrocellulose finish and avoid long term contact with leather, rubber, and vinyl. Guitars produced in 2020 and beyond have the nitro over CAB finish.
So, the Santana III is acrylic over poly. My 2021 S2 Studio (a unicorn, most were 2018 only) is Nitro. Frankly, the Nitro is kind of a pain in the arse with all the concerns with leather, rubber, etc contact. I'd rather they hadn't gone to the Nitro. On the other hand, the S2 rings like a bell, even more than the Santana when strummed acoustically. Prolly not the Nitro doing that though.