All it proves, unless the FAA was watching the replacement, is the mechanic failed to sign off an ops check. How can they say, two or three years after the fact, the pressure test was never actually done? The fact that the records show the inspection was done several days later could simply mean the records people at the airline noticed the oversight too, so they redid the pressure
I don't think that the 787 is on the ELB yet and it certainly wasn't back when this incident took place.
i guess I don't know when it happened. Even with a paper logbook, it would have gone through several Captain's reviews and not gotten caught.