It is a useful axiom; some slaves in the US north in 1850 had more freedoms than free black men in Georgia in 1850.I am not schooled in philosophy or whatever this idea is. If it is a repeat of something else maybe I heard elsewhere and forgot, sorry.
I see freedom and slavery as a spectrum of the idea of agency. There are degrees of ranging from from complete and absolute where I can think and do what I wish regardless of consequence and if there is consequence, meh, so what, I don't suffer from it and you cannot stop me. At the other end is complete slavery where control of my body and even my thoughts have been usurped entirely as in being brainwashed. Along that spectrum there are impediments to absolute freedom, most are voluntary impediments: "I won't (insert activity here), because friends / family / work / society will be hurt / angry / (name it). " going down to increasing coercion and punishment until finally you have no agency, even to chosing to die.
Sort of got this idea from Harlan Ellison's "I Have No Mouth and I Must Scream"
It is also worth noting that many cultures and religions do NOT value it. Modern China has a disconnect: the state absolutely does not value agency of the individual, while traditional Chinese culture only values it to the amount it allows providing for one's family and improving one's station. But many Chinese nationals do not hold to either of those...