I agree that it is much better than saying anything when you are close to them.
It is possible to pass the one person that decides to turn into you just as you pass. It did actually happen to me once. But, it certainly is rare. The only way out of that is to yell far enough away, and slow down, or even stop, if one needs too. I have seen a few peds just turn around into the other lane instantly with no warning and start walking the other way. But I was not very close.
Yes stopping or slowing is a royal pain, but it works every single time. I do pass quietly sometimes on the road bike. Bailey's trike is so slow and so wide, and the dog is so !@#$% loud that I announce a long way away, and somtimes slow to a crawl. It does not matter much in that case I'm only going 10 mph anyway. And I don't mind stopping if it protects me and the dog both. In some cases I need enough time for a dog being walked by an owner in front of us to go nuts when Bailey barks, drag the owner around, or even pull the owner over, right in front of me, face down onto the pavement!!! (It has happened ).
Or depending on the path, it may be possible to pass far enough to one side to even allow them to take a step to the left. I have also noticed that even on my quietest bike, a person walking a dog may not hear me, but the dog can. In that case be prepared for a huge mess of dog, owner, and leash all over the @#$%^&*()*&^%$ place. If I ever walk my dog near a bike path I wear my Take-a-look bike mirror on my sunglasses. I'm never surprised by quiet bikes coming from behind that way.
I suggested it on the forums once, but like anything new or unusual, no one ever understands.