I'm extremely familiar with the capabilities of TPMs (I've worked on deploying remote attestation services at multiple companies), but here's the thing - streaming vendors don't use TPM-based remote attestation. None of them. It doesn't happen. Could it happen? Yes, but it would buy almost nothing - remote attestation is something that's viable in enterprise environments where you can bind TPM identity to inventory entries, and not in the real world where you could just plug in a second TPM on a USB adapter and fake the measurements. And how would you prove the attestation came from the same device that has the reported GPU key? Remote attestation is only useful when bound to other hardware keys, and there's no way within current specs to perform binding between the TPM and the GPU - pirates could just pass the attestation query to another machine.