Umm, that system, the encomienda, was undoubtedly slavery. That it resembled pre-colonial rule does not absolve the Spanish Empire from recognizing it. Everyone knew it was a death sentence, clear enough when they sent English “Lutheran dogs” into the mines, too.

You’re both arguing about revising history when plainly the rule is this: if the colonizer let you live (or even encouraged breeding) it was to extract labor.