Wheel truing

This isn't very accurate though issit.

I know it's been discussed before, sorry.
But, whilst I'm here. I was at a polo tourney and in between games there were quite a few bikes upended with wheels spinning slowly. Someone said this helps re-true them. I was pished so believed them but in the cold light of day, seems unlikely.
True or false?

lol, thanks, I needed cheering up