Very interesting. This is the first "dependency" book in 5e, I think. By which I mean, this is a supplement to Rising From The Last War. Devs have repeatedly mentioned in interviews that setting lines had shrinking sales because you were only selling to people who bought the prior book, and that meant you were on diminishing returns from the get go.
This is probably why we have the notation about it being "a different page count and price point than typical D&D rulebooks". They may be trying it out as a smaller, slimmer, cheaper book and see if the economics make sense.
Anyway, it sounds like an Eberron patch job, and I'm okay with that. Revise the Artificer, update Dragonmarks to be Origin feats, revamp a few lore and setting points, and call it a day. I'll buy that.