On the sacrifice of Tymora, there's a great book on the subject here. Seems like a cool story to me, and I just think I misremembered the part about Lyss, the villain here being Beshaba. Or possibly Darmos.
Writing your propaganda as IG books and accounts works rather well for informing players and characters about events. But it's by no means a neutral account, history being written by the victors, so of course it could lead to misunderstandings. And a server so rich in canon-divergent history is bound to end up with lots of people completely clueless about what has been going on.
And on the surface, that's a good thing in many ways. But to return to the topic at hand, if this degree of general ignorance leads to for example a perceived trend that major plotlines tend to end in a deus ex machina fashion, that would not be good. I really get where LaF is going when talking about a 'basic history knowledge' primer. I've avoided playing characters from Arabel or even Cormyr exactly for that the reason: I have no idea about what's been going on in that region lately, and that's not enough to roleplay it properly.
Worth the DMs time? Maybe. Depends on the amount of work it involves.
In the meantime, we can all make greater attempts at documenting things (from our points of view, of course) with publicly available books! Your character not much of a writer? Team up with one, like in the example I linked to! There are lots of Loremasters and Bards who would like to write about things!