I know what you mean, and if I had to explain it, I would say that it depends on the stress level. There are several images where good misters grab kos by the braids and nothing happens, or when abyusers grab them and they are oblivious. Also, it tends to happen after a while. I see this as something similar to a kid hanging from a bar. At first it will be fine, but if you added some weight, or forced it to stay hanging, well, fun begins...
Well, if you look at it, the Patchouli is holding herself up. Anon isn't pulling on them. One assumes their arms (or pyus) in this case are strong enough to support oneself.