To me, there is more impact, for instance, in Morgoth's betrayal of his brethern, when they trusted him to erect the pillars of the lamps (as according to tBoLT1); his mere a posteriori attack (as according to Sil.) was only a shallow demonstration of his contempt, and affords no comparison
Maybe so but nonetheless Tolkien made those changes for a reason, otherwise the records of Arda's history from TBOLT would have made it into the Silm.
Yes there were a lot of name changes from TBOLT to the Silm, but once again that was Tolkien refining his work as he saw best. If i recall correctly wasn't it giant cats, instead of wolves, that guarded Morgoth's stronghold? I'm too lazy to go get my TBOLT1 and TBOLT2 and look it up.
There were many radical changes such as that, that gradually disappeared from Tolkien's work. For instance TBOLT version of "The Fall of Gondolin" (1917) was, as far as I know, Tolkiens first dabble with his fantasy world, and I really enjoyed that chapter, however, it goes against most of the ideas behind the Silm. Balrogs were not Maia originally and there mass multitudes of them in that battle, I believe Tuor slew a handful of them himself, which would be nice to interpret into the Silm, but because of the drastic changes to Balrogs and such it's not possible.