Yeah, it's basically the PDF Compendium, with non-legacy units added to it, so all these rules have been already available, this just consolidated them. It's being tied to limited releases of faction models. This weekend, for example, there will be a few classic Dark Elf models for limited offer. Definitely a nice treat for collectors, and those with legacy forces. I'm sure we'll see similar things happen with future Warhammer:Legends releases.
One thing to keep in mind, is the rules are not intended for matched play. For example, there are no points in the PDF. But, great for if you wanted narrative play set in the old world.
I am a bit baffled though. If they'd just taken this approach to the rules, rather than reboot the whole universe, surely it would have made more sense? To do this now after effectively destroying the Warhammer World seems odd.
I don't find that part odd. I find waiting two years to do this odd. I think it would have been a bit less jarring, if there was some information like this at launch, about how each of the factions transitioned from the World-That-Was, into the Mortal Realms setting. But, I do like the whole "What they were like", and "What AoS factions are like them" parts, that's super neat.