obstruction should not be an issue. But, how would you make a rule based upon how far away from the plate the runner is when the ball is caught? That would also introduce some subjectivity. That said, if the rule, good or bad, is precisely written, then players should practice to be able to meet the rule until they change it. What I see our catcher's do is receive the ball in front of the plate and sweep tag. I think that disadvantages the catcher somewhat but that's how you avoid the issue.