I opted for the Eve Matter "early adoption" programme hence why I have the latest Matter firmware (3.1) on the available hardware. I cannot imagine that this will be a forced update, I am sure that you would be able to ignore it when it eventually appears on the Eve app around springtime as forecasted by Eve.
For me, 16.2 was a nightmare with its constant connectivity and "no response" issues. Hard to tell if 16.3 has fixed the issue since I am having the same issues, however I have currently disabled the Apple TV as Home Hub leaving the Home Hub designated to the HomePod mini and it now appears to be steady. Not sure if there is a conflict between the Apple TV and the HomePod mini when they switch over to be the "Connected" hub.
Could be, a couple of tvOS versions ago I had trouble with one ATV that has a Wifi connection. Every time when it took over the "connected" status, not every trigger was processed well. Especially those from/to the HUE hub. Only when the wired ATV was "connected" everything went well. Strangely enough, the few moments when a HomePod mini was the master, also on the same Wifi, everything worked fine too albeit slightly slower.
Ever since last versions of iOS/tvOS/HomePod OS 15.x I haven't run into serious problems anymore and kind of forgot to check which device is "master" every week. Version 16 was for me a bit faster too, even though there are more Homekit devices now and some more rules. Maybe HomeKit spreads out all the processing on multiple HomePods and ATV's better now?
I have a couple of complex rules that operate the sunroof. It looks at light levels, weather situation, sun position and time of day and since version 16 it works quite well. Not perfect.
Version 16.3 was installed almost immediately on all HomePod mini's when it was released and I haven't noticed problems so far. The ATV's followed a week later. All devices are setup to do updates automatically.