Rear Cargo Door Vent Question

Today I removed the spare tire carrier from my project JK and I noticed that one of the vent flaps on the drivers side lower corner of the vent located behind the spare wheel is missing. Is this a big deal? Will this allow backwash water on the highway to enter the rear cargo door? It’s not a big deal to replace the vent, but just wondering if that’s necessary. I could also silicon a small cover over the opening if I need to prevent moisture from entering. I’m sure the vent would still function with one less opening back there. Or, not? Anyone know about this or have any advice?

 

Those flaps probably prevent heavy rain or monsoons from dripping in some rain water while driving. Cut a piece of flexible plastic/rubber sheet and caulk the top edge should do the trick.