Una:
Depends on what part of the world you are in. You declare a pan with us you WILL get priority. Calling a Pan with us IS declaring an emergency. The way it was explained to me in simple terms in training was
Pan Pan Pan = we may be in danger
Mayday Mayday Mayday = we are in serious danger
Show me the document!
You
can't declare a PAN. It doesn't exist, there is no such thing.
A PAN call is an urgent message concerning safety, nothing more, nothing less.
That ATC may give you priority anyway, will simply be because they are aware of the poor training level of many pilots and that the will treat their so-called "PAN declaration" as a mayday call - in which case the pilot could have done it properly to begin with and use correct phraseology with a mayday call.