...The reason I ask is to gauge how much value "blank space" is worth. Areas where the DM can go in and paint their own stamp without contradicting established lore. At what point, if any, does detail get in the way of creation. I get there is no one size fits all answer, but I'm looking for at what point does being through become a liability? Or does it not and there is an untapped market for a product that does all the world-building for the DM. After all, APs and setting guides do sell...
What is important here (to me) is not quantity or lore, it is organization and utility.
As a starting block, I would welcome the depth regardless of how I wanted to use the product - but with a caveat.
I rarely use a product as is. I steal from it, but I usually add that theft into my existing game settings. To that end - the more the merrier. I'm using TPPs for inspiration, so give me as much inspiration as you can. If I were going to be asked to run a game in the setting, then I'd also welcome the depth because I feel comfortable that I could adjust around any depth of lore that I wanted to bypass or discord if I was able to understand what was there.
The caveat is that the information has to be accessible and organized. If you just weave little tidbits into paragraph after paragraph of 'stuff' it becomes so hard to find it that it might as well not be there. If you want to sew something, you need a needle. It is equally hard to use one if you don't have it or if it is buried in a pile of hay.
If you have a villager in Village 17 in Region 4 that wandered into town after losing his memory and a Farm Family in Village 11 of Region 1 that is looking for their lost son that wandered off after bing hit in the head by an ogre you need to have a way to connect those dots to each other, and
also a way to lay out the storyline someplace where it is cohesive.
This creates an exponential problem for the size of your described area. The more that you weave into it, the more you have to add to keep it accessible and organized.
Further, for those DMs using the product as is, how much can a DM use? If one party is going to go through the adventure and then the material will be set aside, then a lot of what you write will be wasted, and the more there is the harder it will be to connect the dots. You may provide them with many options to explore, but if there is a central storyline to be followed it becomes harder and harder to find the pieces of it when it is buried under more stuff.
If you like this level of depth, you're better off building the connected puzzle pieces and putting them out there as a unit that a DM can place in a setting, not preplacing them and clogging up a world.