Earlier quoted context omitted.
He also claims that TOTP storage in the password manager is useless. It's only useless if the entire password manager is compromised. If your attack vector is a keystroke logger, or compromise of a single password via a dump, or even someone having written down the password... storing the TOTP is still effective.
Keylogger would still get the TOTP code. Dump would include the TOTP secret. Why write only the password down if you still need password manager for the TOTP code? I think I mostly agree TOTP in password manager is useless, but it's not worse than not having TOTP at all so it's whatever.
It is still effective for the first protection if you store your codes in your password manager, but less for the second. I say less, and not completely, because if your machine is compromised, gaining access to your phone too is only a matter of time. Of course this can be mitigated why proper hardware tokens, but most people aren't using those.