As I mentioned in the SMW thread, for me there are two requirements to consider the game beaten:
1) It needs to display some confirmation of victory - ending sequence, credits, "thanks for playing" etc.
2) It needs to do so because the player actually reached a win condition, not just glitched it into calling up the wrong graphic, entered a "view credits" cheat, etc.
The SMW one is interesting because it does achieve both of those without actually beating Bowser, by glitching the game into a win state. A lot of other runs do this; the SMW one is just more jarring because it just seems to spontaneously skip to "the end" after a couple minutes of bouncing fish and hopping around.
I recall there being a published run for a NES RPG (unfortunately can't remember what it was) that does similar: the player just starts a new game, enters a town, talks to someone, leaves, enters again, repeats this a few times and suddenly the credits roll. Again the game just seems to suddenly cut to the ending scene after a few minutes of seemingly random, pointless actions.
My opinion, though, is that rules were made to be broken, and the "rules" for TASes are more of guidelines. If you can make an interesting TAS that breaks a rule or two, it doesn't stop being interesting.
