The API can set the APM. I didn't see any mention of this being done for the tournament though.
There are quite a few rules dealing with the performance of SC while being interacted with. I'm sure high (for a bot) APM causes issues or just isn't possible.
I would also assume that a minimal amount of actions is preferable to wasted or unnecessary actions. I guess what I'm trying to say is that just a high APM alone does not secure a win.