No, it isn't arcane -- in part because those old manuals are around.

:/ its like saying we know how to program in x86 assembly only because of some 34 year old books.

That wasn't what I meant at all in my original post, and apologies for not expressing myself clearly. But it's good that those manuals are preserved, as they capture the original context of the system's use.

I have another post on this thread where I talk about some uses I've had for old manuals. That's the sort of thing I'm getting at. The GE engine manuals, for instance, aren't arcane in the context of CH-46 maintenance, but in the broader context of printed material they are extremely arcane.