Unfortunately, that one will simply remain a plot hole, as there is clear evidence that Bhaal surfaced way before 1482, as proven by Durge's existence. They could retcon it if they wish (Jergal shenanigans in the background maybe? idk lol), but a rewrite would be an infinitely better approach.
Eh, I can make my peace with the new canon having Bhaal resurrected 20 years before the old canon says so. It's not a big deal. What is a big deal is that the Dead Three should only become active as a unit after the resurrection of each of its constituent parts. Bhaal was slain in 1358, so it's fine if Gorion's Ward died in 1458, 100 years after Bhaal's death.
Jergal shenanigans are
always happening apparently, even though there's little documentation. That dude occupies a
weird place in the divine hierarchy and possesses knowledge and abilities well beyond those of the Greater Gods.
