I don't consider a fork a new version.
You don't, but all of the existing software will do. And that's the problem with hard-forks: you have to convince everyone, or otherwise, you have a forked chain. Which is why soft-forks and no-forks are better.
Which means, that if you make your own changes, without merging them into Bitcoin Core, and without making them in a backward-compatible way, then all users of all old versions will land on a different chain.
And then, at block 150k, you will see your chain with ASIC-only blocks, but mempool.space will still show a different chain with CPU blocks. And all users with old Bitcoin Core versions will also land on the old chain.
I did not see the email.
It is now accepted:
https://groups.google.com/g/bitcoindev/c/Jsv1VYpewuU/m/1CFgHWfSCQAJ