I apologize, I misspoke previously when I said I saw this in a VPI book. I actually saw it in a book from John Berry who if people don't know who he is, has one of the better morph books on BP called Designer Morphs.He is a licensed herpetologist and a legend in the industry. This is the direct quote
Shedding:
Most, but not all ball pythons will go off their food while they are getting ready to shed. This is normal. Some ball pythons however can be so accustomed to feeding that they will still take food if offered to them while in shed. This is not a good practice. If their dry shed skin rolls down their bodies and gets caught up on the food item in their belly you can have a problem. If this were to go unnoticed the dry tight skin roll around them could damage your snake. Wait until they have shed and then feed them.