Superficially, you should be able to make a fully compliant TPM2 on your own like this (unless I’m missing something). The one gap would be that your EK Cert would have to be self signed.
In this case, they bought the actual TPM2 part of the chip from Infinion, so it might already have an EK Cert on it.
I skimmed and had some wishful thinking that they just made a cheap off the shelf chip do the job of a TPM2 by slamming in an existing TPM2 implementation.
Is there any evidence that it wouldn't be possible - does Windows have a list of approved EK certificate authorities it expects?
The only reason I could think for this would be DRM, but I wouldn't expect this to be a requirement merely to install the OS (the un-approved TPM would still be good for any non-DRM uses, and would be useful in VMs where the TPM is already emulated by the hypervisor).