Thanks for clearing this up. Last year I was shopping for used phones and looking at S8/S9, and getting very confused when I saw S21 starting to pop up. "How many of these did they make, anyway?"
S10 was the last of the old numbering scheme, they changed it in 2020 (with the S20).
Tangentially related, Reminds me of this: In Los Angeles there's a few very prominently displayed billboards at a shopping center for the Galaxy S4 that has somehow remained up [1]