I made a thread about this practice a year or so ago. I agree. But what has really clicked in for me about throwing the football is how the elbow determines so much. Throwing a football is like a flat serve, so your elbow should be coming at the ball when you serve flat. The football throw really helps with this and of course the wrist as well.
I was really struggling with serve for a while..took me so long to get it back from when I was younger. But now that I am consistent again, I can go for flats and this knowledge of the elbow's role really helps.
Please help TT Member BruceD get a wheelchair so he can play tennis again - http://tt.tennis-warehouse.com/showthread.php?t=496820