The section title is correct: they're authenticators implemented in software, not relying on a TEE/TPM or any other bit of hardware for storing the keys. Apparently these don't run on on your CPU architecture and/or operating system of choice, but that's another issue. The claim of "they are stored on hardware tokens, there does not seem to be a way to have privately generated software keys" is incorrect.

Perhaps https://github.com/bodik/soft-webauthn is closer to what you're looking for.