His concern is whether he can prove the rifle was assembled prior to the ban, and if the upper was built AFTER the ban that would not be possible.
I'm going to agree with the theory that the upper is pre-94, and that the rifle is legitimate.
Whether it is worth the $1300 or not, well, that's an individual decision (to me, no).
The autonomic nervous system provides for involuntary muscle function - the work of breathing, digestion, and so forth. On some folks, that's a pure waste of ingenuity.