Ssh keys are much simpler than the PKI cert infrastructure. This has advantages for development, as well as bug resistance. But it means ssh expects every server behind the same hostname to use the same SSH key.

You can't get two (well functioning) TPMs to have the same key. They come with their own, un-extractable* and unchangeable keys built in.

*TPMs claim this, it is probably not impossible to extract keys just incredibly difficult and requiring specialist knowledge.