I'd say this happens about 20% of the time. Amped tomatoes just make him change into a whiny kid, but no matter how many times he is hit, he remains un-popped. Going out of his range causes him to revert to a Troll.
Only thing to add is that one time when this happened, I used an armored innertube to knock him into the water. When he landed in it, he had 5 or 6 rapid-fire splashes all in a row, over the span of about half a second. I have to speculate that the number was dictated by how many times I tried to pop him.