Section 215 includes the lovely clause that you are not allow to mention that you have received one. The fact that Apple is saying they haven't in interesting because if they stop saying there is a very clear inference that can be drawn. Think of it as a canary - when you see that line dropped in subsequent reports you can assume Apple has received one, even though they won't be able to say so.
Section 215 allows you to lie, and it is considered the truth. Our lovely government thinks it can issue an edict that says "this is the truth now, when you are asked and you say that this never happened you are telling the truth."
In fact, this pronouncement means nothing. If, or should I say when, they got a request under section 215 they also got permission to say that it never happened. They are just taking advantage of that.