The benchmarks are from GCP, where the vTPM is implemented in the hypervisor rather than on something that's plausibly an 8051[1]. Doing this on actual client hardware is going to be a bunch slower.
[1] Typically ARM these days, but most system vendors aren't picking TPM vendors based on performance
What mjg59 says. The benchmarks are against a vTPM, that was what I had access to, and it's the environment I'm implementing the RATS side in.
Worth adding that not every outbound connection needs to go through the TPM (IMO). It's for the handful of services where the machine-identity actually matters, a secret store, or an HSM releasing key material onto an attested confidential VM, in my case.