I'm not sure he has looked at too many benchmarks. 3440x1440 is not that much more difficult to run compared to 2560x1440. I know this because I've gone from 1080P 144Hz to 1440P 165Hz to 3840x1600 160Hz. The "numbers" look big, but it's not that much of a loss.
They also bring up the vRAM of the 3090 as if 10-12GB of vRAM is a limiting factor at 3440x1440. He's wrong about having to buy the best every round. You don't need a 3090 or TITAN equivalent every generation, especially not at 3440x1440.
DLSS is a non-factor at this stage since it's really not common in many games yet. When it is, then that's a useful counter-point, but it's not there yet. GSync/FreeSync are great but they aren't magic. 40FPS still feels like **** compared to 100FPS, though 40FPS with GSync is much more tolerable than 40FPS without it.
Regardless, his point is that you need to buy a flagship GPU in order to run 3440x1440. He is wrong.