It is extremely possible that the frames have some kind of foam seal on them and the silicone weatherstripping is to stop water and crude build up on the upper edge. Water turns to ice and can be very destructive on an RV. Ice on the upper lip could act as a wedge and unseal the window from the siding.
I would silicone that section of missing seal.
All that said, it appears the term Quality Control is either not in RV maker's lexicon or is poorly understood. You will find novelty in your RV's construction, both in good and bad examples. In my TT, I found a lot of cool ideas implemented, and also some shoddy workmanship on a few items. You have to either have some handyman skills or have one on speed dial to own an RV, IMHO.
