TPM does contain a secure key store, not just fixed function encryption and signing operations. Unless it's fTPM, in which case the storage and device firmware

TPM does contain a secure key store, not just fixed function encryption and signing operations. Unless it's fTPM, in which case the storage and device firmware attestation is handled by firmware - but it is still key functionality. You really don't need anything particularly special to make a cloneable module that supports all TPM 2 functionality, it's just that the available ones are not and any other would not get certified. The ring -1 functionality is firmware attestation. It must be supported as per spec. So no, TPM is not just a chip or just a key store. It is much more than that hence the blobs that handle it had security bugs.