"MEST bodies are somewhat irrelevant - it's the 'thetan' that matters, not the container it chooses to be in for a certain length of time."
That's total ignorance of the reality. If only the "thetan" matters, why is the prison planet a problem then? It shouldn't matter wether the bodies are owned by the prisoners, when the bodies are irrelevant, right?
"And what's much more important is whether that is actually 'chosen' or 'enforced' (ie, being pushed through a DT and having memories wiped."
So you're saying that Scientology believes that slavery of the body is irrelevant, but slavery of the thetan is not, as if there was no connection. But in reality, there is. The ignorance of that connection is what psychologists call dissociation:
https://en.wikipedia.org/wiki/Dissociation_(psychology)
"Dissociation is a concept that has been developed over time and which concerns a wide array of experiences, ranging from a mild emotional detachment from the immediate surroundings, to a more severe disconnection from physical and emotional experiences. The major characteristic of all dissociative phenomena involves a detachment from reality, rather than a false perception of reality as in psychosis."
I think that the dissociation of the thetan/ISBE by declaring the body it owns irrelevant is the result of a psychological trauma. Evil provided evidence that the ISBE can be enslaved. The response to that was to disconnect ISBE and body as if they are two different realities, which they are not. It's like having a car accident and then saying that you weren't in that car, so you don't feel to be part of the trauma, while in reality, you are and suffer from the consequences.