Actually if anything (though I donit think it does, so I doubt I'd try and use it), that scene SUPPORTS R=U. Rinoa doesn't die, so there is no paradox, meaning no argument against R=U. Furthermore the ridiculously low probability of what happens with Squall saving her almost points to the event being fate, Rinoa COULDN'T die, which is exactly what R=U states.
EDIT: Lilliputian Hitcher I would agree. If one were trying to argue what the canon story was, then R=U seems very unlikely due to Ultimania. Taking the game itself as an isolated story, with all its gaps left to be filled, R=U IMHO becomes a quite plausible, and attractive way of filling them.