That is likely because either VLAN tagging was turned on by default in TOS3.x or a lot users turned it on and therefore routed Lan traffic through the CPU anyway
and that is what

Since I implemented that hack with vlans, which pushes all the traffic through CPU, I had no issues at all with WiFi roaming. So I’d recommend it.
is replicating.
A a better solution of course would be if DSA or bridge driver would communicate with the switch’s ATU with updates of MAC address on upstream ports.