Heavy Duty axles actually have oil bearings instead of grease bearings. Those usually start around 8,000# axle rating so you won't see them on a regular RV trailer. I've never had an issue with an bearing setup being "full" of grease as long as the seal isn't leaking or grease isn't coming out of the front. Easy Lube spindles are designed to "fill" the cavity where the bearing are. If the seal does leak you are probably going to get grease on the brake shoes and you will be buying new shoes. To work properly, the cavity doesn't need to be full for grease bearings to work properly. I pull the hubs and check my bearings the same on my trailers as I did on my old cars that had front grease bearings.
I would have the dealer check them since it is a new trailer, but some dealers don't have people who really know, or care about trailer bearings and brakes. If you are knowledgeable about the bearings and brakes, you may want to pull one yourself and check it out.