I don't think it's heavy for skill positions. They claim it's just their overall rating, which is made up of all kinds of stuff. This year, for example, they have several linemen in the top 25 recruits in the nation. I'd imagine if some of those dudes were in the transfer portal, they'd rate higher than the guys below them at skill positions.
Also don't think you're looking at the stars quite right. They do have Iowa with a 4 and a 3 star, but us with one 4 star and zero 3 stars. Those guys had stars in high school, but, for whatever reason, they have them as zero stars now. Could be they know what they're talking about and all those guys flamed out. I'm hopeful they don't and Rhule knows much better and found some diamonds.
Anyway, I try not to take any of it too literally as it's clearly an inexact science, at best. But I do think it's the best barometer available top to bottom for that kind of stuff.