A) It was never intended to be a comprehensive setting guide, it—like the title says—is about the Sword Coast, with a brief overview of other areas.
B) Not everything has, or will have, a public playtest. This isn't necessarily a bad thing, it's just a thing.
It's a non-setting-specific book, that uses the FR IP for branding purposes to make it sound more interesting than "Monster Manual 2". In the same manner that Xanathar's Guide will not be setting specific either. The naming is just a conceit, and they'll probably use characters from other setting for the same puposes whenever they introduce other setting via their APs.
Considering that 4e straight up rewrote the lore on lots of things, this is a quibble at best. But, again, this isn't a FR-specific book.
Yes. Pretty much all non-AP books they release are going to be similar in that regard (much like 1e's Unearthed Arcana, Oriental Adventures, Dungeoneer's Survival Guide, and Wilderness Survival Guide). This way it appeals to more people than just those that DM or those that don't DM.
While Xanathar's looks like it will be suffering from several flaws, these aren't any of them.