Hm, maybe I'm misremembering, let me check.
Arabel, Marsember, Westgate- Cormyr.
Baldur's Gate -that's on the coast, along with Mulmaster, Elturel.
Daerlun -Sembia.
Then there's also Tantras, Zhentil Keep, and Hillsfar.
So no one area gets a lot of coverage, and in fact, it basically skips Waterdeep and the North (no Icewind Dale, Baldur's Gate, or Silverymoon here).
So it's pretty spread out, I mean, Baldur's Gate to Westgate is a big swathe of land, but yeah, I'll agree, it probably doesn't cover more territory than the SCAG. It's still a pretty packed book for it's size though, which is roughly the same page count as SCAG.
The difference is, FRA is DM-facing, with things like treasure tables, art objects, gods and priesthoods, unique currency, updates to the setting, etc., and the SCAG is more player-facing (or at least, neutral-facing). A book like that might not get made in today's market, I dunno.