In answer to high school team who have the SS signal "looks" to the pitcher....I know of at least 3 in our area. One of them being MY team.
We don't like to have MIF out of position because they're running to the bag while the pitcher is throwing to home. We found it much easier to have a signal to our Pitcher to look 1 or 2 or 3 times. All he has to do is do that, then throw his pitch. He knows his MIF will be where they need to be, he doesn't have to "wait" while they get back in position, and he doesn't have to think about the runner as much.
And not that pitchers are dumb, but we do think that it takes a mental burden off of them. They look back a certain number of times, and if they don't need to try to pick him off, they throw to the plate. At the same time, they don't have to try to think about how many looks they did the pitch before, and try to do a different number of looks. Our SS remembers what he siganled, and he changes it up.
One of the other teams that I know does it has won our big school divison state championship something like 3 out of the last 7 years, and been in the finals all but one of the last 7 or 8 years.