Right, that makes sense and is consistent with what I've said all along. If, without the "correct hammer and trigger" and/or by removing or "manipulating" the disconnecter you get FA (which includes a double fire), then you are in violation of the code section.
Otherwise, you are not. Meaning, if you don't mess with the disconnector (or remove it) and have the other semi-auto parts, you are OK with just the bolt carrier in your upper.
Again, don't do it.
BTW, ATF's admonition that you should not have an M16 bolt carrier in your rifle is akin to my constant admonitions not to do it. However, you are confusing this admonition with a RULE or some recitation of existing law. That is an incorrect position. If you want to say that it is advisable not to do it (as I do) then fine, but if you proffer that it is the law then you are wrong. It's not. You have simply picked out "bolt carrier" from the above text and proffered, out of context, that it alone in an upper is illegal. That is not accurate.
It is accurate to say, as I have all along, that if the carrier IN COMBINATION WITH OTHER PARTS OR MANIPULATED PARTS ( like the disconnecter) creates FA, you are now breaking the law. If not, then no law is broken (just my admonition).