Well, they EOL’d their early–release WiFi-7 router that came out before WiFi-7 was even finalized, and simultaneously released one that they have spent an extra year debugging. Presumably they fixed the firmware bug that fixes the synchronization problem, or switched to a different implementation. It’s a really bad idea to buy early products like this since.

This is standard tp-link policy. They release a model, give it almost no support, then release a new revision a year later with incompatible hardware and then the old one is never updated again.

If a product never got a firmware update during its support window, was it ever supported to begin with?

It was EOL from the factory. 0 updates. But other routers I "own" receive updates regularly so I guess I won some lottery.