I am not a collector, but I believe the line is drawn at reproduction parts. If a Luger has all Luger parts (not repros), even if mismatched, then i consider it "original". It has all original parts; maybe not the ones it left the factory with, but few if any military weapons do.
So when I see a seller advertising their Luger as "all original", I'm not concerned if it has a mismatched toggle axle. I know they mean "all Luger" parts; not soft Chinese castings.
IMHO, too much emphasis is put on matching numbers. To me, that is a Red Flag that somebody has been playing mix & match...