I think this is partially WotC's fault. The storyline picks up right after Descent Into Avernus, which was a problematic module at best. Many theorise that Baldur's Gate itself was supposed to be dragged into Avernus, but WotC chickened out and made it Elturel instead. The whole first act of DIA is set in BG for no reason, other than people love/have heard of BG. So Zevlor telling us that they're refugees from Elturel means almost nothing.
Especially because the full title of that module is "Baldur's Gate: Descent into Avernus" xD
