And it still is perfectly reasonable behavior. Any distribution that decides (perhaps as a consequence of this) that on any boot process abnormality the default response is to enter an immediate reboot loop would be called crazy.
I agree with the logic that by default the OS is doing the right thing without any changes to support this model.
Itβs still looks perfectly reasonable, just PCR should be fed with some value before that, maybe a hash of initramfs file? It seems to be reasonable as at this moment the state of the operating system differs from the one properly booted, which seems to fit the idea of secure boot.
This way it would be possible to still unlock LUKS with a pass phrase but not access TPM keys locked for configuration when initramfs shell is not running.
That's not to say that an improvement can't be made as we move towards a future where TPM+LUKS might be the norm - just that you can't retrospectively claim fault on an OS that doesn't claim to support that.