I don't believe so. I think Quickleaf's only belief that they might be connected is that there were some planar entities in SoW that are also planar identities in the Realms. Thus the question of whether there's only "one" planar entity of each type in the multiverse, which would thus mean SoW was a "part" of the Realms (since they share the entity.)Did Ed Greenwood write any of the Scales of War adventures?
I do not believe that personally. I think every entity is one of an infinity group of them that each and every one of us can use at our leisure. Otherwise... we would have to assume that the Tiamat that is considered an Overlord trapped within Khyber in the Eberron setting is the same Tiamat that has been trapped in Avernus and almost escaped in the Tyranny of Dragons Realms adventure is the same one that appears in Red Hand of Doom. But just that just makes absolutely no sense... story-wise especially.