Basically anybody buying parts, who just wants the parts, knows how to avoid triggering single carrier provisions.

There have been a few rare cases in the past where certain fleets were acquired with their pilots, but that's a lot harder today because I'm pretty sure that now you would have to take the pilots in seniority order, even if not qualified on the type. Unless it was a very senior fleet (eg. 777), it probably just makes sense for an acquiring carrier to train/hire internally. Although in the case of NK all the pilots are qualified on the type.