The TPM-based measured boot isn't part of the UEFI secure boot specification. It's a separate TCG spec. Secure boot doesn't use the TPM and doesn't support remote (or even local) attestation.
Interesting. It still worries me to see it in the "Windows 8 Platform Integrity Architecture". Are you not worried about it, or just pointing out that it's not relevant to the topic at hand?
Lots of (especially cheaper) machines ship without a TPM, so it's difficult for anything to explicitly require it yet. It's something to be concerned about in future, but not an immediate issue.
