Since the internet relies on satellite coverage, it's possible that coverage in these areas is lacking. At least Carnival is warning you ahead of time.
I'd stay in the Pre Check line for the sole reason of not having to take all the stuff out of my bag. If I'm on a business trip, I have 2 laptops, a tablet, plus a CPAP.
I once flew out of an airport without PreCheck. I didn't have to take my shoes off and got to just go through a medical detector, but I still had to take everything out of my bag. It was a small airport with only a single lane.