Yes. The documentation for the begin…
method says so, at least sort-of:
You may nest calls to this method safely, but you should always match each call with a corresponding call to the
endGeneratingDeviceOrientationNotifications
method.
This kind of interface is usually implemented using some counter. Each begin…
method increments the counter, each end…
method decrements it. The notifications are sent as long as the counter is greater than zero.