That was only for first-party games. And even them, it was more of a soft guideline than a hard rule, they said "1 or 2 years, we think".Funny story about me completely misunderstanding MS with the Xbox...
I just sold my Series X because I wasn't using it much other than to play Fallout 76 and I have a One X that will play it almost just as well. The only game I was looking forward to was The Medium and I thought, oh I can just play that on my One X. I thought there weren't going to be any Series S/X exclusives for 2 years! Oops.
I do have a PC and I'll try it on that, but I guess I missed some MS communication somewhere. Now I need to see what other games will be Series S/X exclusives.