Grandparent's point is that you're stretching the meaning of the term to a level of generality that applies to everything, therefore meaning nothing in particular.
Your point applies to French just as much as English: Gaulic Celtic speakers poorly adopt Latin after getting bull rushed by Romans, then mix in Frankish terms when the Romans' former allies take over; or how about Sicilian: a mash-up of Latin, Greek, Germanic, Arabic conquerors.
You have to go pretty far to find a language which isn't a fusion of other languages that results from different peoples entering into extended contact.
'Creole' is a word that only appears with its current meaning and history in the last 100 or so years, grandparent is simply preserving that particularity. Nothing more.
No one in 1200s Europe thought English or Sicilian were languages not worth engaging with as actual languages owing to modern racial connotations.