While I don't doubt that this happened, according to the memorandum issued, approval is given as follows:
One of those exceptions, listed in paragraph 1(d) of the Policy Memorandum (see Conditions and Exceptions), allows for activities under a special use permit (SUP) that specifically authorizes launching, landing, or operating an unmanned aircraft and that is approved in writing by the Associate Director, Visitor and Resource Protection (ADVRP).
So the information can be given by the superintendent of the park but it must be obtained from the ADVRP directly.
So the superintendent themselves cannot give permission, they can only convey the permission given by the ADVRP. At least according to their own memorandum.
To:
Doubt or not it happened (several times) and it was done on the spot so apparently the superintendent on location has been given some form of allowances to approve such without involving anyone else on the totem pole.