Wish I could assist you with a knowledge nugget but I’m fairly inexperienced with pumps, let alone ones that cover the balls as well. Personally the sensation I get is an uncomfortable pull only on one section of my penis, right by the base, but generally, in medicine a spongy feeling is tied to fluids since I doubt you’re getting an infection from pumping. Unless you don’t clean it, in which case you might want to clean it.