but TOS Spock DID disregard it. Hello: Leila Kalomi?
He didn't seem to care so much about T'pring honestly, only reminded of her when he got "sick" and needed her. She wasn't innocent but she wasn't all to blame either, I have to say.
still, we don't know if this Spock is still betrothed to anyone so let's wait for when this plot is developed a bit.
He didn't care about T'Pring and T'Pol had no interest at all in her betrothed. While many must just marry who they got paired with it seems social expectations don't always match reality.