Not trying to nitpick, but I think this makes it more clear.
Also, I might (HTBT) point and say, "that's obstruction," when it occurs. I certainly wouldn't yell it (in an attempt to sell a call...as no selling is necessary), but it might be a good thing to do as you will be letting the offensive coach/team know you saw it. Then, when the play was over, I would have that "simpl(e) and discrete," conversation with the catcher.
By and large, I agree with your post.