AA smatters award PNRs with "AWARD" "AA only can change" etc. messages, plus all sort of automation scrubbing it and ensuring that the rules are followed, which is the real reason that AA will not allow any other segments, even though Sabre will be happy to accept and ticket (in a separate ticket--segment select) .

As far as visit xxx pass, it will be issued in a separate PNR; a ticket paid with miles is no different than one paid with cash, check, or credit card so it qualifies as transportation on AA as required for the visit xxx fares.