You do have a decent point there, but you do bring up an interesting question, if the Anti-Italian riots in Split are substantialy more violent, thus causing the Italian reaction.
However, it all very much depends on what happens if Italians decide they do want to make a fight out of it, and actually stage an armed intervention. That would force the Yugoslav goverment in Belgrade to realize that Italians could have a much larger appetite and that they are coming for quite a bit of land, something that Yug. Gvt. Really can not let go, especially since that would definitely destroy any faith that Slovenes and Croatians had in Yugoslav/Serbian monarchy, and are pushed into a war they really do not want.
On the other hand, while it seems that Italy does have a substantial advantage, situation is not really as bad as it seems for Yugoslavia. As I said in my previous post, Yugoslavia could call upon over 1 Milion Men in 1941, and that number could be acomplished here as well, or somewhat reduced, with all of the fighting occuring on the Yugoslav territory, so they should have at least some familiarity with it. In regards ti combat experience, both sides should be about equal, but in regards to the morale and motivation of the men involved, advantage is certainly on the side of the Yugoslavs, especially Croats and Slovenes from the territories in question. To these people the Italy is coming in as a vulture to pick apart their homes, not to mention that Italians are the ancient enemy, hated Venice reborn, coming to slice off and annex rightful Croat/Slovene lands. Not to mention that while relations between Serbs and the rest are not particulary friendly, they are not outright poisoned as they were IOTL 1941, where non-Serb soldiers simply stayed at home while invading armies dismembered Yugoslavia.
Considering all these things, as well as terrain, which is difficult even today to go through, it is possible that this ends up in a bloody stalemate, and drags out until one side breaks, and my money is on Italians to crack first.