I am not sure if your post is meant as more of a question or a comment....??
I suppose lots of water collecting in the flutes of a barrel could change harmonics of the barrel and affect POI and consistency.
Other than that, I personally have never seen my zero (300 yard) change during a rain storm. I have never detected a POI change in the range at any distance in the rain. Nor any accuracy impacts (abnormal or unexplained major group changes). The only differences I have been able to see are the pressure, humidity and tempratures associated with the storm. So long as I compensated for the current conditions properly, things have been spot on. If anything I shoot a bit better in a slight rain because the air is cool and the sun is hiding. This all but eliminates any mirage and is easier to shoot better groups. A little rain is a good thing (IMHO) where a heavy rain makes visibility difficult and water gets all over your lenses.