I Love playing in FR in The well trod areas cause there’s so much lore and previous lore and history. Wherever you are, if you need something in This Swamp, there probably is something already written. My players are in The Mere of Dead Men, and with official and Dungeon adventures it is loaded with stuff to look through and play with or also disregard and ignore. WotC has made a point of being much less specific on lore recently, because their goal is to make things more open. I don’t really care for it, but unless you’re fixated on true To official published for some reason, all that detail Is still available, in my world the last 500 years of FR history is just yesterday when I need it.
but to OP point. Yep, they’ve gone vague...because it’s all fictional history so it doesn’t matter and you can do whatever the fork you want. They are very much trying to empower DMs by implying that these are not fixed real places, these are just helpful ideas of places you could run a game.