Looking at it from the perspective of the BO - he told her his routine before she moved the horse.
As a BO- I find it very frustrating when people do not listen or think they will change what was told to them during the interview process.
I have to agree.
The amount of turnout, per the OP, was stated prior to her moving the horse there. The BO does not need a talking to, the OP needs to accept what they moved into or move her horse (giving proper notice).