I wouldn't think the BM has that much of a choice. I tell her what to show and when, and she follows orders. lol Musta been in the military at some point.
I have her set to those days and then I go through thursday/friday and enter the green horses to make up the difference. (when I do remember to show, which is... not often)
Is it mostly because the BM can only show one discipline a day? So if you have an eventing horse set to d/xc/sj on monday/tuesday/wednesday for example, then if the horse is green in dressage it only gets to show dressage one day that week?
As Foggie said, the BM does seem to do better with SD horses. At least it seems that way, as the majority of my show horses are SD geldings. I'll have to pay more attention when stallions get entered.
As far as the BM goes, she does have a tendency to enter horses who aren't ready. Seen plenty of horses she's entered that came dead last. It's less of an issue now since the showing payouts have been increased.