You can't implement remote attestation without a full chain of exploits (from the perspective of the user). Remote attestation works on Android because there is dedicated hardware to directly establish communication with Google's servers that runs independent (as a backchannel). There is no such hardware in PCs. Software based attestation is easily fooled on previous Android/Linux.
The call asks the TPM to display the signed boot chain, you can't fake that because it wouldnt be cryptographically valid. The TPM is that independent hardware.