Your team will go for it on 4th down if they are in hurry up mode, that may have been what happened - that is the only time the AI will go for it on 4th down without a rule.
Even if I don't want them to? Does that mean I can't have hurry up offense and not go for it on 4th down?
The purpose for you going into "hurry up" is because you are out of time to play normally - you are trying to catch up, so you are taking all the chances to try to catch up. The idea of being in hurry up is that you don't have time to give the ball back to the other team.
In this instance down by 10 with 4 mins to go so I went into hurry up just as the 4th down came about. Just one of those things I can't account for then. I'd have punted. Could have got a safety and an 8pt touchdown to tie. :) Always optimistic.