Graham, yes, sorry,I was going from cafe to cafe and didn't double check.
But anyway, it's not an 'obvious flaw' in the classic, because the advice is not ordering you to step into the opponents legs even when you attack from the outside. If you advance, step into his legs. That's why I said it was "Xingyigarden" because it's common sense between XY players and no one comes out and jumps saying "What if I step from the outside". Well, come on...then step to the same distance from the outside. Common sense.
And the "stepping into the opponents leg to make him unabe to regain his balance" is in all the XY quanpu out there. It's not a 'classic' ) between quotes. I know, it's not in the "Theory of Unification" from the Ten Thesis, which is one of few the writings you accept. But it's out there in every single Xingyi Canon. Ask your teacher.
Throwing stones? naaah...well, at least you didn't say I was being rude to you