Actually,this rule does not apply to them as they are not Hellborn but Charlie is literally the Queen of Hell and Stolas is an Ars Goetia
So,yes,while they were born in Hell,they do not count as Hellborn,which is why people were outraged when they found out about Stolas and Blitzø,calling Blitzø a "lowly imp" because he is an ordinary Hellborn,while Stolis is an Ars Goetia,who are like royalty but not really