Only use the timing play signal when 2 out and runner on 2nd?

[Matthew F]

I have been told/taught to use the timing signal with two outs and a runner on 2nd. If the purpose is to "inform" each other of the possibility of a timing play, why shouldn't it be used in other situations?

1) With 2 outs and R1 at first, there is a potential timing play if the BR hits for extra bases...

2) With 1 out and runners at 2nd and 3rd, there is a potential timing play if the BR is forced and a play made on the runner at 2nd...