I've been going to NUFC games since the early 80's (not so much since around 2003 when I moved away and started a family) and have never known NUFC fans sing it.
For some reason, I associate it with teams like Man Utd and FA Cup semi finals in the 80's
It's just a different tactic to make it appear more credible.
Ultimately, he loses no face if he comes out later to say the deal was close, but ultimately fell through.