Yes, I agree that there is a scale, but I don't think that is really the relevant point. That "unthrowable" stability is the expression of a certain kind of practice all by itself - that would be a little bit closer...
"unthrowable" stability. I have a view on this but I know it would be different to yours and I wouldn't use such wording to describe it as I feel it leads to more confusion and indeed delusion than it does good.
However it does remind me of a little story from my past.
My girlfiend at the time wanted to visit her friend in a certain 'no go' area in north London as she was living with a guy who was a master of some martial art. This art she said practiced 'unpenetrable' body.
That did make me smile. She said it was Ki based and what she had been told and we discussed it.
Anyway, move forward to me being in the guys house waiting for her to return from the kitchen where she was chatting with her friend and husband and a group of guys from his school. It was called Kateda as I recall.
One guy came out from the kitchen and brought me a book to read and then another came and asked me if I would like a drink and then another came and sat down and proceede to talk about martial arts. I listened and acknowledged them but was taken by a strange type of reverence they all seemed to be giving me.
Finally my girlfriend reappeared and was ready to go and everyone came and bid us farewell and even insisted I leave with a present.
This bugged me. When we got home it dawned on me that something must have been said in the kitchen that I was unaware of so I asked what had been said.
She told me that the men had been showing her some Kateda and she had done what I said and they hit the floor. On asking her where she learned that she had told them I had taught her it.
Wow! Now it all made sense. I shook my head and laughed. "Why do people do that?" I thought.