By cutting off at 8th Gen and TPM 1.2+2.0, they’re cutting off a lot of current and high end systems built by enthusiasts, while supporting far slower and inferior PCs.
That’s the problem. No one’s arguing they’re chasing off cheap Celeron, they’re trying to get rid of even some Threadrippers and multi-socket setups, that could have 128GB or more of RAM, for “performance”.
So, what's in those generations that might actually matter to Microsoft? As you say, it's unlikely to be about performance. Is it some instruction set, or feature flags? It's unlikely to be about virtualization capabilities, as Intel still happily sells the newest chips "differentiated" to be virtually challenged. Did those generations introduce some crypto algorithm/primitive that Microsoft doesn't want to go without? A new system management mode? On-die microphone?
Intel sales is desperate to stop brand loyalty vanishing, processors losing relevance, while Microsoft is trying to recuperate costs on cancelled Windows 10X code. Those are suspicions I have.
The “only the latest Intel enable $use_case” cliche is their default marketing narrative. Microsoft or AMD or NVIDIA normally don’t do that.
I don't understand the logic of your response. It's not like Microsoft will brick machines not eligible for Win 11