It’s not slavery then because the free will is taken into account in the construction of the relationship.
I think that’s why US history textbooks (or at least used to) make a distinction between slavery and indentured servitude. They seem the same but one is entirely involuntary whereas the other is a contractual relationship between parties in some fashion.
It’s not slavery then. It’s an agreement. Unfair power? Sure. But there’s an exchange of goods and services in some way.
Good thing it worked out for them then. Doesn’t make it a template to follow.
People do it though. Different example: “My parents beat me on a regular basis and I turned out fine. Kids today are weak. A good whipping will make them strong.”
The first thing is fine. Even the second thing is an opinion anyone can have.
But the third thing as a recommendation is a problem.