I think you're correct about the importance of the context in which the expertise exists in.
But even so, I think it's clear that with more broad documentation, we are in a better position to pick up the expertise of the past.
So in the future, all the wonderful, nutty youtubers that keep alive old arts and give demos would be especially invaluable. Not just in clarifying specific techniques and knowledge, but by demonstrating a general approach to problems that existed at the current time.
I've been watching all sorts of things the past couple of months like this: People making vacuum tubes, repairing vacuum tube equipment, older mainframe technologies like ancient versions of MVS, machining parts on equipment from the '30's.
None of it is how-things-are-done in a cutting edge factory or step by step directions on how to reproduce an important cultural artifact, but from the perspective of future people, it will be a valuable aid to gathering that context.
One I'm particularly reminded of is Clickspring on youtube who is building an antikythera mechanism. Even though we have the partial artifact, so little is known concerning metal working technologies of the time that it seems to be an anachronism completely alien to its time of origin.
His approach is to explore what technologies would make sense to a working craftsman of any era (which also could be surmised to have existed in the era). It's interesting to watch and it has apparently born fruit in terms discovering academically important information about the device.