In reply to Martin W:
I'm not fulling understanding what you're asking re: the AB knot, but...
Impact forces shouldn't be significant in caving, but there is the all too easy possibility of higher than factor 1 falls and the subsequent forces. Relative to the question, I assume you're wondering what difference the knot type used might have? I'd suggest very little!
They do indeed. In relation (a very oblique one!) to the OP I'd guess none; though examples of what you mean may help.
I'm not trying to condemn the AB by the way. It's a good knot. Some of what I'm arguing is pretty subtle stuff and opinion based.