False.
Not every slave was the same, and while there may be a few that fit the description of “not thinking about freedom,” that is usually because freedom was never granted to them.
The average enslaved person in the United States was subjected to extreme physical conditions and horrific physical abuse. Even if they were content with their housing and food situations, they were overworked and not paid at all.
There are many historical pieces of slave interviews and books written by former slaves that detailed how they escaped from these situations and the many different ways they could do it.
There is also no such thing as a “kind slaveowner.” buying people and treating them like property is an unkind thing to do regardless of how you treat them.