As I mentioned in the previous post, Yes they can.
I didn't ask whether they "can" I asked whether it was part of the statute or an FDA internal regulation that says they "can". I would think the law that created priority reviews would say that such reviews are to be completed on time so I would suspect it was not part of the statute.
You seem awfully eager to defend the most corrupt agency in the government why, bureaucrats are the lowest form of life (well them and politicians) and FDA bureaucrats are the lowest form of bureaucrat.