I would disagree on that. It depends on how regularly you upgrade. At the zenith of my PC hardware enthusiast career, I was upgrading prolifically; often twice or sometimes even thrice within the same generation. Now that I'm older and don't game as much, I upgrade on a much slower cycle (although to be honest this X99 based rig that I'm on now is beyond long in the tooth). For someone like me, going with a Z790 motherboard plus 13900K setup makes a lot of sense because I will not upgrade again for at least 3 years. OEM buyers will keep their machines for even longer.Buying the Z790 platform would be dumb this December. No upgradability. At least, Z690 owners can get a nice rush of endorphins from their investment when they upgrade to the 13th gen this year or in the next few years.
And you may say, well the x670e platform will offer a substantial upgrade path so why not fully commit yourself to Zen 4 rather than the current 60-40 split in favor of Raptor Lake? And to that I'd say, by the time Zen 5 or Zen 6 becomes available, the x670e chipset will not be an optimal solution for those CPUs and they will be held back in performance and features.