Yes it is more or less after the ball has gone, a follow through as you say. (I have just been swinging my arm in the office here to replicate what I do, now I look a right fool).
I don't do it all the time though, it just happens every now and again. Basically, I hit the shot then realise I have rolled my wrist over afterwards, it was just something I felt more with the heavier handle as opposed to the lighter handle.
"Tennis is just chess with balls....zugzwang"
"The older I get....the better I was"