They may have been recruited by Urnfield elites and not given the advanced swords or the swords were not mass produced by this point. The ships themselves that Sea People's used seem to be related to Urnfield
They also speculated that some Egyptian artist simply preferred to use the old sword types in their depictions, even though they weren't used as often any more. We don't know for sure, but what we know is that Naue II swords were used and made it to Egypt, both with the invaders and mercenaries, traders later.
In any case, Gáva in particular had a true mass production of Naue II swords. Their core areas are filled with finds from an early point onwards.