This article in the New York Times discusses how dirt may be somewhat good for kids, and the reason why kids are always putting everything in their mouth is actually an instinctive mechanism to make sure they get that nutritious dirt.
Well I'm all for letting your kid explore, and we definitely don't freak out about how Miles puts everything in his mouth, but check the second paragraph of this article:
"When my young sons were exploring the streets of Brooklyn, I couldn’t
help but wonder how good crushed rock or dried dog droppings could
taste when delicious mashed potatoes were routinely rejected." [emphasis added]
It's subtle, but the thing is, when a parent says something subtlely, especially in regards to bad parenting, they are totally trying to hide the truth. So when this lady playfully implies that she saw her kid trying to eat doo doo, she really means that when she wasn't looking he ate the whole log.