The debate has been had many times on these boards on whether resale restrictions affect RIV's sales. I'm skeptical, and think simpler reasons like newness and COVID's impact on RIV sales are much more likely explanations. But, it's certainly debatable.
One potential reason I had not thought about before, but would be another simple reason to explain the difference in PVB and RIV sales numbers - you just need more points at PVB for most room categories. By my math, if you set aside the Penthouse 2 BRs, Bungalows, and GVs, equivalent accommodations at PVB can range from 15% more points at PVB to up to 45% more points at PVB for a full week. So, last month PVB sold about 34% more points than RIV - how much of that is simply because, your average PVB buyer, when sitting with their guide and determining how many points they wanted, looked at the points chart and said, well, I want enough for 1 week per year in this room - oh, and maybe I want to make sure I have enough for preferred or theme park view every other year if I bank or borrow a few of my points. If you're sitting with a guide and looking at the RIV points chart, you simply don't need as many points.
As a side note, I imagine the guides really like that - look at the points chart, are you sure you have enough points? Oh, and do you think you might want the theme park view sometimes? I think this is yet another reason while we see a points chart at LSL with as many preferred/premium views as they can reasonably justify and a points chart that, won't quite match the Island Tower, but will give a lot of us on these boards a bit of sticker shock.