It is well your fault if you do this.
Yes, it is completely my fault for doing that in battle arena.
But what if the game does the same thing on its own? By accident it either spawns a ton of creatures all at once or it keeps on spawning to the point where the game becomes unresponsive. (e.g. creatures get stuck in freeplay and can't reach portals or other creatures, so they never get removed. And the game keeps on spawning creatures.)
It's just an idea, a simple safety measure. Is up to the devs what they want to do with it. (A cap of 1000 or something very high. So that it is only reachable when something happened that wasn't supposed to happen.)