I only counted 2 you crazy guy. 5 is an exaggeration...if you're talking about the battle I was apart of (Red vs. Green)
2 horsemen were killed by the defenders when they spawned basically in the defenders infantry scrum. 3 more horsemen spawned about 10 feet away from there and were able to ride away without getting killed.
I was speccing the match and witnessed 5 attackers spawn in the defender's side of the map. Would be nice if that didn't happen again.