Yet they DID change the interpretation in the first passage (because they felt that private machine gun ownership would be too alarming), further reducing the degree of fit between the 1st clause, and the right itself.
I don't read it that way. From my limited research, Heller was the first one to actually address the prefatory clause directly. Miller came close, but stopped just short. Everything else has been suggestive but not definitive. They have time and time again listed the RKBA with the other individual rights for example. So they didn't change the interpretation, they established it.
Further, we don't know how they feel about NFA and private fully automatic weapons in private hands as that wasn't the issue before the court. They can't hear a case on abortion rights, and veer DIRECTLY off on recreational drug use. They can only leave bread crumbs for another lawyer to follow and put that issue before them phrased in the same way citing the case they left the bread crumbs in.