I know this is last year's post, but I thought I'd pipe in.
I noticed the gaps in the caulking on our 2014 178 on the spoiler and I had heard, and seen, that there was a large hole for the wires that wasn't very well sealed, so I removed mine to re-caulk it. I also installed a rearview camera so I ran the wires under the spoiler over to the screw rail on the right and down under.
The wire hole on mine is small and very well sealed. In fact, as was mentioned, I don't see a strong motivation to seal the spoiler that tightly. Maybe just the top. I'm kind of hesitant to make it "permanent" with silicone seeing how it's really not protecting anything. Am I missing something? Maybe the screw holes need some sealant.