I think it's important to distinguish between physical choice and psychological capability. I find Barconian's example problematic, and your therapist's example too, because they don't seem to separate the two things.
Having been harmed as an adult in a literally captive situation, I can't accept a statement that someone being abused had no choice when they could physically have opened the door and walked away. However, I can accept that psychological impairment kept them from making a different choice, even when other choices were available.
Feeling psychologically unable to leave a situation depends on history and mental, emotional, physical and practical resources. It also depends on ability to go into denial, dissociation and derealisation. This is where I see one of the differences between being literally tied and being psychologically tied. When you're literally tied, dissociation comes as a necessary reaction. When you're psychologically tied, it also plays a part in what choice you make - it enables what you feel is your only option.
I'm not saying the person is to blame for that any more than they're to blame for things like thinking abusive behaviour is normal. But it's necessary to recognise the active part that things like dissociation play, for me at least, because without that it's incomprehensible that someone wouldn't take action in a situation where their children are being hurt.
The difference I'm trying to get at is between being unable (physically) and feeling unable (psychologically) to make a different choice. I don't say being psychologically unable, because I think there are still choices, subconsciously. One of those subconscious choices is to stay numb or unreal. If there weren't subconscious choices then nothing could ever tip the balance and no-one would ever leave an abusive situation that they had been in.
I think it's unhelpful to oversimplify the psychological aspects as having no other choice, because obviously - in a literal sense - there were other options. To me, that doesn't help understanding. Better to represent it as much more complex, which it is.