I don't see what you mean by that. I think Brandon might have made a conscious decision not to ape RJ's style, and for all we know Harriet supported him in that. She was the editor, after all, and she let it all go through.

It's not really THAT difficult to stilt your dialog and prose in the way that RJ did. I think it's overblowing things to say that it's some sort of grand skill. RJ's skill is in his world building and intuition about politics and warfare, in his ability to keep so many plates spinning and still remain almost perfectly consistent, not in his ability to write old-timey dialog and description. That's something any initiate writer ought to be able to do.

Claiming that Brandon, an established author with multiple best sellers under his belt, is less skilled than an initiate writer is just plain bias against the guy that you're most likely harboring because he ruined your favorite series.

Which is a fair cop, I'm not totally happy with the job he did either, but to call him a bad writer based on his use of contemporary dialog is kind of weak. It was just a bad choice, not poor skill.