I agree, players of any sport don't mess with anything when things are going well. Common sense and superstition both enforce that rule. The point for me is that when a great player goes a bit off, he or she is sometimes seduced by the idea that there is something wrong with their original approach and therefore they need a new one, which seems unlikely to me.
In McBeth's case this would mean for instance that without realizing it he has actually stopped doing what made him successful and what he needs to do is watch video to see what he is doing wrong. It doesn't mean he should start doing something completely different because his "old" approach is now somehow no longer a good one.
Obviously injuries and or age can cause an athlete to need to tweak their routine but I wouldn't suspect that Paul's putting woes are attributable to either one of those.