It's all extremely stupid. The original idea was to prevent sellers from exporting critical US military technology which, I suppose, makes sense.
Somewhere along the line, though, some brain-dead moronic left-wing bureaucrats decided that if there's such a thing as an optic that the military uses, then it follows that ALL optics & associated mounting bits, screws, etc. are US military technology, regardless of the place of manufacture, intended use, etc.
To show the extent of this idiocy, the ITAR rules consider a second-hand, British-designed, Taiwan-made, BSA "Sweet 22" scope (only useable on .22LR rifles, and only for target shooting) as "US military technology".
I even tried to buy a round, hand-held magnifying glass and was denied export from the US, as it, too, was considered US military technology.
Just goes to show what can be accomplished when Liberals are running the show...