Ruin Explorer
Legend
You surely mean FR between Greyhawk and Mystara. FR has much more cultural differences in close proximity than Greyhawk does. And much less overall material detailing how the different countries interact with each other. Ok Greyhawk has a little less detail generally I give you that.
I definitely do not But I am referring to 1E/2E FR compared to 1E/2E Greyhawk, primarily! Very little was written about GH after 1E, and it all makes it look even more simplistic than it was. The FR actually has a similar thing - 3E and onwards FR has way less detail about cultural interaction and so on then 2E did. You read 3E or later FR stuff and compare it to 1E GH stuff and it's more similar. But there are entire FR books in 1E or 2E which are basically descriptions of culture and politics and trends, with relatively little game information (usually some spells/magic items though - some of which will fit with/into the cultural stuff). People sneer at that now, often brutally sneer, basically spitting on it, but at the time it was remarkable. GH's countries may have conflicts, but they don't have much of a sense that they evolved together, and many seem to have simply sprung into being. It's not as bad as Mystara of course, where it seems like someone just clicked some new hexes into place with an entirely novel and alien culture (which, in isolation, is cool, but in the context of surrounding countries is bizarre). Even the FR is far from Taladas, let's be clear on that, and GH isn't miles down the line towards Mystara.
Just as a note, Birthright was more up the Taladas end. Ravenloft is way down the Mystara end but it's entirely conscious and in-setting so works.