Never worked a game under MY Book rules.
I understand the philosophy, but don't always by into presumption because you just know.
Did you ever have a coach tell you a runner MUST have left early because there is no way that runner could have gotten to 2B that quick? Or because no one can steal on that catcher? Or that pitch must have been illegal because (fill in blank).
I'm going to have to see the effect of the OBS. I have seen players run right through a fake tag without hesitation. Did I call OBS? No, because there wasn't any impediment. Did I still warn the fielder? Oh, yeah.
By definition, there needs to be some affect on the B/BR/R for OBS to be in effect.