Yeah and I think there's a real question as to how hard Cosmere fandom will cross over RPG fandom, and also whether Cosmere fans who aren't currently RPG players will start with this RPG.
This is one area I do think has the potential to be real issue, because fundamentally, the Cosmere fandom (rather than the more specific fandoms of Mistborn, Stormlight, etc. separately) is built on obsessive lore collation/memorization. Like multiple chapters of a book might only make much sense if you've read entire other trilogies or more, which aren't even set in the same universe. For Cosmere fans this is a selling point, one they clearly really enjoy and will defend to death as a positive (often using some kind of questionable "cross-marketing is an inherent good because it might make the author money!" logic, but that's a different issue), but it does mean that, even compared to Star Trek or Star Wars, the fans are often unusually lore-obsessed and lore-theory-focused.
And more than being character-driven or even conventionally plot-driven, a lot of the books are focused essentially on "lore reveals", which further weights things in this direction (even if said lore reveals tend somewhat to be "Actually the thing people in the setting think is good, is bad!" or vice-versa).
It's possible it won't actually matter much at the table, but it does worry me a bit.