That little bumpout is where the router used to cut the vent hole didn't "complete the square"... Not surprising at any RV manufacturer's line...
Just wait until you need to pull one of the 1.5" vent stacks and find the "hammer hole with all the broken edge splinters" where rather than use a hole saw to cut a 1.5" hole, they just "slam a hammer through the OSB and wiggle it out until the pipe slips through".....
