So there is no such thing as covenant technology then?
Does that mean the hoover dam may have been made from beaver technology? - someone saw a beaver build a dam and thought (thats a good idea, i'll see if I can do the same).
If the UNSC
can't rebuild every aspect of the device using current technology then it cant be called theirs, reverse engineering can only go so far unless you develope a complete understanding of the underlying tech and then build the device from scratch, The infinity still has Forerunner tech because the UNSC is as of yet unable to fabricate an ideal replacement. Think they ripped that idea out of Stargate- the US Airforce using the wreckage of to Go'uld death gliders build one prototype hybrid space capable fighter, most of the ship was Go'uld tech that had hidden safeguards and when the test pilots take the ship out into space the alien tech locks the ships controls on a course back to its Go'uld planet of origin and in doing so the occupants die of old age in the centuries long trip. Course later varients of that fighter are 100% human built.
The Hurogok the covies use are not the same as the ones recovered from the shield world Onyx/Trevalyn, the covies Hurogok may have started off as blank slates and accumulated their knowlege from the recoverd Forerunner relics the covies found, the Onyx ones had been operating the forerunner tech of the shield world since the time of the forerunners, either it was the same ones or they recreated each other if they are capable of ageing and dying.