Citing a 20 year old game that got a few bells and whistles plonked into it and still having to play it at 1440 to get good framerates isn't exactly what i'd call impressive. Cute showpiece and all but it's a gimmick at best, yes i tried it and while it was obviously different looking it was still a 20 year old game with a coat of paint splattered onto it.
It didn't get a few bells and whistle plonked on. It got a full path tracing engine. Have a look at the excellent posts by @Rroff.
Gpu grunt would have nothing to do with it, they would still be rendering the same image via dlss albeit at different framerates. If artifacts are shown on one gpu, assuming the gpu isn't faulty then theres no reason why it would be absent on faster gpu's, they're all still using the same tech after all.
I beleive DLSS partly uses data from previous frames. If it's not getting enough frames then you will get artifacts.