I'm curious as to why the stroke order of 力 is different to the stroke order of 九.
One page I found (力 and 九 stroke order) theorises that the reason is because 力 has "touching" strokes and there is a hook that "points" to the second stroke, so it could not itself be the second stroke.
This seems to be a decent theory, though I'd like to know if anybody has a concrete source proving (or disproving) this rule. It does note that it only applies for cases where the strokes touch, so it does not count in cases like 刂.
Any insights?