It doesn't really matter in practice, because the discipline around contract law is (typically) based on reasonableness of terms - I can't sign TOS that say I'm

It doesn't really matter in practice, because the discipline around contract law is (typically) based on reasonableness of terms - I can't sign TOS that say I'm a slave, nor will TOS apply if such a clause is introduced at a later stage. Regardless of whether terms are changed for administrative or product reasons, what matters is the reasonableness of terms imposed on the other party.