Because lawyers. Apple currently is under no obligation to release the rational for their decision. If they publicly tell him why, he can challenge it much more

Because lawyers. Apple currently is under no obligation to release the rational for their decision. If they publicly tell him why, he can challenge it much more effectively. The apple NDA is possibly too broad to be enforceable and given that ALL of their competitors are allowed access to the developer system, gives them no traditional protection of trade secrets. Id est, It gives them an unintended benefit of controlling the public story (and thus some degree of market forces) about their products, but does not keep their market competition from peaking inside. If they divulge the rationale, and he challenges it in court it would upend their (and lots of other) developer programs, or at the very least cost them lots of time, attention and goodwill fighting to preserve it.