Tread,
If you really like one part of a coupled entry and not the other, and the other horse takes action, the race is ruined. Your play is gone.
And then you have the scratch issue.
And of course the shenanigans that take place with uncoupled entries.
Personally, for every one race that is ruined because I can not figure out what might or might not take place with an uncoupled entry, I find many more to be ruined when my value disappears due to a coupled entry.
I would prefer they not expand the coupling of horses.