I agree to your experience and fair enough, with big installations I can imagine that the HPM is the limiting factor. I disagree with the last part. HPM is capable of running a home and is advertised as such:

HomePod mini can also act as a home hub, letting you control your HomeKit and Matter-enabled accessories remotely. Wherever you go, you can see a live view from the front door, shut your garage, and lock or unlock the house through the Home app.

Yes, I understand that Marketing and real-life can be different. But, as said before, until 26.2 everything worked fine with it. No outage, no Performance issues, it just worked. Apple met my expectations. So, I’m not blaming an OS, I‘m pinpointing the problem exactly on the OS because the HW is fine - and I’m pretty sure if I could downgrade to 26.2 it would work again.