No, your problem is that you apparently have an ASA rule book that is five or six years out of date!
(Or, possibly, you looking at a rule other than ASA's.)
They removed the phrase "about to receive a thrown ball" several years ago- it no longer applies. A fielder gets no protection from an obstruction call if she is positioned to catch the ball, but impedes the runner BEFORE gaining possession of it.
It's sounds like this was obstruction. The base award...doesn't sound right. A coach could have questioned the umpire about the award. If he said it was "his judgment" that the runner would have reached home, well then, that's his judgment (it might not necessarily be good or sound judgment!) and you're stuck with it. If he told the coach something like "obstruction is an automatic one base award"...then you have a misapplied rule. The next thing out of your mouth should be, "I want to file a protest".