Just to be clear, my advice was not to punish him (sitting in the office at recess). It was to put out the immediate fire (to remove him from the situation that triggers his disruptive behavior 90% of the time) short term because he is in a crisis (suspension) mode.
I totally believe and encourage evaluation to try to determine and assist the underlying behavioral issues, whether they be sensory related or some other behavioral issue.
My advice was for the here and now until she can get the assessment and help because IMHO, sitting in the office for the remaining 3 weeks of school is better then dealing with suspensions. And if this is what has to happen short term, I would in no way relay to the child that he was sitting in the office as a form of punishment. I would let him have some activity to do (coloring, reading, laptop) while he is in the office too.