If the service wants to make sure the keys can't be copied then it will need remote attestation for either the whole system or just the TPM (what you called "ke

If the service wants to make sure the keys can't be copied then it will need remote attestation for either the whole system or just the TPM (what you called "key attestation") to ensure that the client isn't cheating. If it's only the client that doesn't want the keys to be copied they have any number of options for that and no attestation is needed. I assumed your article was promoting the former as the latter really isn't interesting at all.