I can attest to this, as the smoothing clearly isn't only on the 4k 3090s. However, the issue is actually as 'big' as that r0ach guy is making out to be, because it's the difference between a hit and miss shot (which is what marketing usually proclaim that their mice make you aim better, however with the current ethic this isn't the case anymore). I am saying this out of personal experiments as I've tested a wide variety of mice, and not based on testimonials only.
I see you post a lot on these boards a lot, and you seem to be a very even-handed guy, however for this case I think it's actually wiser to pick the 'better' side. Your standpoint on the realism of higher dpi being a huge marketing factor can be equally as well refuted due to the fact that 'top speed' (high dpi) isn't really what makes the mouse desirable--in the sense that mitigating delay would be.
P.S. I hope the Rival doesn't have this delay/smoothing issue, although I think it does based on everything I've read so far.