fwiw, I really don't understand what you are objecting to.
Just that I didn't like your previous attitude.
Just that any fan is different, and that - as SPCR pointed out several times - small rpm deltas make more noticeable SPL deltas.
So, some rotational figures may give us some clues, but I think nothing more definitive (without any further verifications).
I would add that if the SPCR noise floor level (10-11dBA) isn't enough quiet for you, more probably that not anything currently can be (any piece of equipment tested here scored above): but it's not the main point.
Eventually, even if I can never tell to anyone "how", or "how much" to ear, I may legitimately ask for some more caution, prudence, when writing down judgements/appreciations about equipment never experienced, in order to not unnecessarily decrease the SPCR S/N ratio (just for the sake of future readers of such words).
Last but not least, the Sapphire card should emit about 4dBA higher than the ASUS at idle, IIRC.
In case, not a huge difference, but neither a negligible one, I mean.
I hope I've been much more understandable now, thanks for your patience.