Wuxia in General
Simply being 'visually fantastic' should not (and does not to me) qualify a work as Fantasy. I am going to argue that while the visuals of these movies defy the laws of physics, the intent is not to show that these warriors have supernatural powers, but instead to imply that they are skilled enough to make it appear they are acting supernaturally. Its a form of visual hyperbole.
I am not excluding the possibility that there are such movies which are in fact fantasy, but just walking on air should not qualify them as on topic. I would go on to say that the visual hyperbole itself should be off topic, as it is not intended to be taken as fantastical.
Wuxia with a Sole Bona Fide Fantastic Element
To allow questions about a work with a limited scope of what about that work can be discussed (in the comments, the bamboo fighting scene from Crouching Tiger is used as an example), puts us in a paradoxical position. A question that may or may not be related to a fantasy or scifi element would be moved to another site if it was not obviously directly related to a fantastical element - before an answer could make that clear. A question apparently about a fantastical element would be allowed to stay even if it turns out it wasn't.
We also do not move questions with answers that prove not to contain any scifi or fantasy element.
To clear that paradox we either need to classify any work with a fantastic or scifi element as wholly on topic, or limit the works we accept as on topic to only those works that are intrinsically scifi or fantasy.
My position is that wuxia is not intrinsically fantasy (though a particular story MAY be), so should be considered off-topic. Crouching Tiger out, Kung-Fu In Space (a hypothetical film) in.