[latk]

They were not asking for consent in the meaning used by the GDPR. They are merely "asking" you to agree to updated terms, i.e. their contract with you.

GDPR allows processing of data under various legal bases. They use consent (opt-in) only for things like accessing your camera. For sharing data with other Facebook services, they rely on a "legitimate interest" (opt-out) instead. In theory, you might be able to object to processing under a legitimate interest, but they make it rather cumbersome. Which processing activities they perform under which legal basis is actually well-explained in the privacy policy, if you manage to find the correct section (it has a rather labyrinthine structure).