That does look a bit odd but yes it's likely for weather protection. I just keep my spares open in the box and really have not had any issues. If the connectors are good gold plated contacts it should easily handle normal outdoor humidity and temps. I like the rubber plugs but in high humidity I could also see it trapping some moisture in the enclosures. My outside box is good enough for weather protection even with thunderstorms that drive rain sideways. I installed 2 vents
with foam inserts and one is connected to a thermal fan control. Comes on above 85F. Never any problem.