You have got me wondering if it something we are taught due to our UIC teaches/allows NCAA mechanics. I know that most I have worked with use it. But I am not sure if all are aware of it.
I had to go get my ASA book and recheck it. It is not there. The two outs to signal IFF off is there but not for timing play.
I find it helpful. Most of the time I remember there are two outs but I have fell asleep a couple of times and the signal brought me back in focus. I was on the bases.
I'll be sure not to use it this weekend.
This is another good point to go over in pre-game --all umps have to be aware when a timing play could affect the scoring of a run or not.
On this one, I like the reminder with two outs. Could happen as Mike says so pre game it. there I straddled the fence.