Welcome Kymco Owners!
OK, I'm a little late to this party...I have also thought the cvt cover gasket does nothing if you only ride in the dry..I suppose it could prevent rain water from entering if you ride in the wet. As for oil dripping from above and getting into the cvt cover? It would be obvious with oil pooling up top if this was the case..but where would it come from? It's theoretically possible to way overfill your gearbox oil...and have the excess blow into the airbox and then drip out..but even that is suspect. And the OP said his vent tube from the gearbox wasn't even connected to the airbox.Now maybe the vent tube was draining onto the top of the cvt cover?I would still say a leaking oil seal inside the cvt cover is the most likely culprit. Those seals prevent engine oil and gearbox oil from leaking out..they eventually wear and will start seeping/leaking. If it's oily near the back and not the front I'd zero in on the seal in the back for the gear oil under the clutch.