Yes, someone would buy a 3090 for 4K or 8K as you suggest, but testing at these resolutions, will only show that a 3300X has the same performance as a 10900K (-1,5% at 4K, same perf at 8K) The majority of the Tech press declared 10900K as the Gaming King and I would imagine that is based on their own experience and tests, but surely was not 4K average fps testing...
I mentioned the new GPUs mainly to highlight that 1% of the miniscule advantage Zen3 will have vs 10900K at this test, will also be due to PCI-Expess 16X gen difference.
720p testing shows some indications when GPU is not the limit and is useful if you know what to take from it (depending on the game/level used etc). Also why the argument regarding latency/cache/CCX etc, for whatever reason an architecture is better at something than another, in the end it is better. It is like saying that the Rendering superiority of the Ryzen does not count because mainly it is from SMT vs HT performance difference, does it change the outcome that Ryzen is better at Rendering? Also i would imagine that most of the game engines are more optimized for Skylake than Ryzen architecture, in the future with the new consoles and with Intel stepping away from Skylake this will change also.