I understand TPM is quite an important tool for security, but a lot of the updates not being offered should not be related to TPM. Not offering updates to people who bypass TPM on Windows 11 and also providing information on how to bypass TPM seems strange to me. Looked around for an answer, but there doesn't seem anything official.
Does Microsoft say they won't provide updates? The KB Doc about installing on unsupported systems says:
Devices [..] will no longer be guaranteed to receive updates
They want to use capabilities of modern TPMs in future updates. That's why there are those restrictions and why it is not recommended to install on unsupported systems. In case you have a PC without a compatible TPM, those new features won't work on your PC and therefore you won't receive those updates. But they aren't actively kicking out computers from their update mechanisms, as far as I know.