I suppose the inverse would be starting with a device that offers TOTP/MFA, and then making your password-manager/vault somehow available on that same device. In either case, bringing them together makes it easier for an attacker to compromise both at the same time.

On reflection, I've never actually put my (personal) password vault on my phone, but that may be less of a conscious security stance than fulfilling a millennial stereotype, where certain tasks (like big purchases) are reserved for "a real computer."

Closest I've gotten is having my USB backup keychain in the same pocket, so I could get to it in an emergency, but it's inconveniently air-gapped.