Been Sic in two aircraft which called mayday for legitimate, flight threatening reasons (Like a bald eagle through the windshield at 17k) and was PIC in one where I lost an engine At fl 210 and called Pan Pan for inability to maintain altitude over ORD on a crappy day when I couldn’t get a word in edgewise to Chicago Approach.
on all three occasions, the first words out of the controllers mouth were: “Are you declaring an emergency”...
So over here, the phraseology doesn’t seem to mean a lot without some mention of the “E” word...