Index Imperium 1, p117. The ability 'Terminator Armour: Models in this unit have a 5+ invulnerable save' does not appear on the Deathwing Knights datasheet. Even though they do have the Terminator keyword, without that listed ability, does that mean technically they do not have the 5++?
I did not see anything in the FAQ that addressed this. I doubt any reasonable opponent would enforce the loss of the 5++, but in tournaments they certainly could.
I don't see it addressed in the ITC packets either.