I played around with a recent image I had from a vacation.
My normal edits with filmic HR off.
Changed the brilliance highlights to 32.61% (until it showed super nova, no issue at 32.50) and turned on filmic HR (default settings).
Adjusting the white fulcrum in the color balance rbg to +15 had not effect. Going -10 made it worst. Auto picker picked +2.84, but it looks the same.
But the change that did managed to had a positive effect was reducing the filmic HR transition to 2.
I can even use 100% in brilliance without super nova.
While not a fix, it might further help reduce the occurrence super novas(if someone turns ON flimic HR and goes too high on brilliance highlights). I tested in a few images I had. If someone can confirm that using 2 for transition helps on their images too, then I can do a PR.