I was able to ask the Author my question:
Me: “La Haye Sainte Final assault scenario, how do you count the independent units toward brigade or army breaking?
Seems like if the independents don’t count for those at all, the French can only win by taking La Haye Sainte.”
Adrian McWalter: “…all the ‘British’ units count as one brigade in total, hope that helps”
So I think that settles it for me, two brigades for the ‘Allies’, follow normal brigade/army break rules.