I suspect that you may be trying to get us to overthink this topic, or to point out that we may be overthinking this topic. Either way, here are my two cents worth:

  • The 10-15% guideline likely came about as a result of learned experience through feeding young ball pythons. I personally have not seen this size recommendation being made for anything beyond hatchling or young adult snakes. Citing Ball Pythons: The History, Natural History, Care, and Breeding, by Dave and Tracy Barker, as my source, "the best meal for a ball python is a single rodent that's large enough to make a barely discernible lump in its body that last for two to four days." Through trial and error of seeing what size lump results from what size rodent, I believe this to be where this site's 10-15% recommendation for young ball pythons came from.

In my own, limited, experience with young ball pythons, I have found the 10-15% range to generally produce the kind of lump that the Barker's describe. This is why I personally have found it to be useful. It certainly should not be a rigid rule though, as feeding decisions should be specific to the individual snake.