[greymule]

In ASA, if they are trying to return, they MUST be tagged

That's one of the key points involved in this play. While it's certainly true in OBR that a runner in the vicinity of the base must be tagged, I'm not sure that's the case in ASA (see OP). The case book gives a play where the runner misses home and F2 immediately appeals by touching the plate. No mention of the runner having left the vicinity.

In other words, in the play in the OP, if F4 had (a) stepped on 2B and immediately appealed to the umpire that Baker had missed 2B, or (b) while diving to tag Baker had said, "Ump. He missed 2B," then the appeal would nullify the run. This is only because (the way I understand it, which could be wrong) ASA permits an immediate live-ball appeal at the missed base.

Incidentally, in OBR, the runner at 2B in this play is of course out (tagged off the base), but it's a straight time play with the runner from 3B—not a force. And there is no later appeal for missing the base. The run scores and cannot be nullified. Of course, had Baker advanced to 3B without touching 2B, an appeal at 2B would indeed nullify the run.

The apparent prohibition of a "fourth out" appeal on a runner who has not scored is yet another wrinkle unique to ASA. With their rule change a couple of years ago and the change in ruling on a case play, I don't see how the appeal can be allowed.