At no time did ATC refer to a possible Mayday but instead used the terminology of "declaring an emergency".
I wonder if this isn't done deliberately. If all of a sudden ATC would utter "mayday" while the comms have a bit of static on them, the aircraft involved might think it was a mayday from another aircraft and shut up.
Sort of the same thing as we have with departure/take-off. To avoid any confusion, the first time the word take-off is used is when ATC clears you for take-off. Until then everybody talks about a departure.