A/C: "Mayday,May..."
...a few seconds later...
TWR: "Do you require any assistance right now?"
A/C: "Negative"
If the crew could do it over again, they most probably wouldn't use the M-word again. Training instinct kicking in? Like the crashing 777 at LHR, using the training callsign for their mayday call
And just maybe they had more important things to focus on, than the optimal phraseology?