With a mechanical device, you don't know the dimensions on press fits, you don't know what the aluminum was heat treated to, you don't know the silica to aluminum ratio and how that affects thermal expansion, you don't know what lubricant was used, you don't know what blend the fiberglass insulation is, the list goes on and on. It's not possible to obtain 100% knowledge without the drawings. At best, you make assumptions about material processes, what a reasonable press fit would be, occasionally you can spark test to make a guess at material composition, etc.

There isn't a "holy grail" (1) mechanical equivalent to a hexdump where if you grind at it long enough you achieve 100% knowledge.

(1) Obtaining a complete set of original drawings is, but unlike a hexdump, you can't get the drawings from the finished product.

Exactly this. My father is a civil engineer who's now in his early 60s, and he recently got to work with colleagues much younger than him.

He told me that said colleagues didn't know some trade-related stuff which hadn't got covered in university courses (like how to reinforce earth ditches when digging in mountainous terrain with probable heavy rains) but which was paramount in keeping the work going (not much that you can do once a ditch collapses because of heavy rain). He told me that in this instance he had instructed his younger colleagues on what was the correct procedure to take, but he also told me that he's got other professional secrets that he's not ready to share just yet.