Good move (perhaps)
At long last, broadband suppliers with own-brand routers won't be able to bamboozle potential customers with meaningless (to most people) strings of numbers and letters. If company A offers Wi-Fi 6 but company B only offers Wi-Fi 5, you know at a glance which one is faster.
Except that if A's router's implementation of Wi-Fi 6 is crap you might still get better throughput with B's Wi-Fi 5. And then there's the question of do you really need that bandwidth when the speed of your copper/fibre is often the limiting factor? Plus, on top of all that, you might not actually have any kit that supports Wi-Fi 6 (or even 5). Still, this is probably a good move by the Wi-Fi Alliance.