I think I’m with both Ed McW and Moreno Roncucci on this. The indie ethos is about laser focus and relating everything to actual play. It’s a reaction to (as they see it) the era of splats written by people who generally didn’t play filling books with “fluff” that was largely designed for reading enjoyment and not playing enjoyment. And, as I see it, it was really only the most hard-core, lots-of-free-time fans who could pour through the mounds of material and find what was gameable and use it. That’s always astounded me, honestly.

I mean, look at all those tabs in your Rogue Trader corebook. And there’s THIRTEEN more books in that line!

Also, I’ll again point to BWHQ, who produced Bloodstained Stars for BE, which is 100% in-game fictional material.