From your last paragraph it seems apparent that you aren't comparing like with like. If you're comparing the information provided in the FRCG about a region to the information provided about a region in a 2E regional book, then it's absolutely certain the 4E book is certain to come up short. So does the equivalent 3E FRCS, or the 1E boxed set, or the 2E guide.
But those all had regional sourcebooks coming afterwards. 4E hasn't.
(Of course some will say there might be such books, but in that case: Where is the "more accessible because of less info" argument going then?)