I've witnessed a couple cases where things went from hiring a lawyer, to sending a letter, to a stalemate where legal bills started getting so expensive that the only winners were the lawyers. When you're dealing with a big bureaucracy you can't count on them giving up at the first sight of a letter from a lawyer.
The legal route also takes time and locks any further conversations into the speed of both sides' lawyers. Time matters in this case because this student needs to get registered for classes, so anything that could stall that process needs to be weighed carefully.
I wouldn't be surprised if this issue magically goes away as soon as the publicity comes around to local news media and/or some alumni with connections.