Are you sure about that? I've reviewed the ITAR regs in some detail and I don't recall coming across that. Do you have a reference?
In Part 121
121.10 "Forgings Castings and Machined Bodies clearly states this :
Articles on the U.S. Munitions List
include articles in a partially completed
state (such as forgings, castings,
extrusions and machined bodies)
which
have reached a stage in manufacture
where they are clearly identifiable as
defense articles. If the end-item is an
article on the U.S. Munitions List (including
components, accessories, attachments
and parts as defined in
§ 121.8), then the particular forging,
casting, extrusion, machined body,
etc., is considered a defense article subject
to the controls of this subchapter,
except for such items as are in normal
commercial use.
I bolded and underlined the section you can't dispute . Doesn't matter its a "chuck of metal " to some people
Anyone can see even a raw AR forging is "clearly identifiable" as AR part