I believe the poster didn't mean this as "denigrating", and were rather referring to the caloric contents, where "hot water" implies minimal amount of calories.

Of course, making a proper broth takes time and does put some nutritional value into said "hot water" (as do onions fried on oil/butter, sauces you add and potentially sugar), but that doesn't really change the fact that the will be minimal amount of calories in that.