Eh, fiction is all about lying. The question how good you can write the "no-no, this is THE REAL TRUTH" - stuff^^. And one of the recurring theme of the series is, that you have to discover the lies of your forebears, so I can still forgive them some hickups. People lie in this games, a lot.
No, this is not NPC's lying, it's just the developers being more interested in whatever the latest idea the writers came up with and deciding that is the new canon, never mind whatever happened in other games.
This is not an attack on Larian or the writers. That approach gives a lot of freedom to the writers to do whatever they want, which makes them happy... but it means world-building is uneven.
