Very reasonable, but there are two things that make me sceptical that teams are created from real players.
It very often (almost always) happens that a new creature is released and you see very high level versions of that creature in a battle within minutes. Sometimes it even occurs that you have three opponents of this creature and sometimes you even see them in a battle before they are released.
Opponents in PvPs almost never level their creature to the maximum possible level. There is no plausible reason to send a creature with level 17 or 18 instead of level 20 into a battle.
I do not think that such a big amount of real players is so silly.
But this is only another assumption.