Yep, that's been going on with all the team events. =\ I get someone to enter crappy horses on single-horse teams in my driving pairs events when I spot one sans teammate.
That's been an ongoing problem that never seems to be addressed. Most people running team events will enter crappy horses in teams with single horses to keep those who try to take advantage of the situation from winning.
Sometimes, when a single horse enters team events, it will win, which it shouldn't. So when someone enters a single horse, many people will put another on their team to keep from exploiting a bug.