I have never understood that argument. Engineers/huragok are forerunner by design. They were built by the forerunners. The 'offspring' of two engineer contains the knowledge it's 'parents' did (IIRC). Therefore, by some nature, EVERY engineer in existence would have knowledge of forerunner tech. Maybe ranging from "OMG it was on a shield world" to "It knows how to make forerunner washing machines" but they'd all hold some knowledge about forerunner tech.
Huragok are living computers, as they gather more information (about thier lives) they must make more room for it, so they delete older data (tech) so when two engineers build another and do a data transfer, the newest huragok will have memories of previous huragok generations too.
Huragok are sentient, living machines, and like any other machines they require maintenance, for all we know huragok may not have been able to self maintain (probably as a failsafe in case they were charged with maintanance of an AI which went rogue) so that engeneers require maintenance from the forerunner lifeworker caste.
With the time difference inside Trevelyan, the huragok could only be say 5 years old, or less generations than the ones the cov found which probably have thousands of generations.