So an arahant is beyond cause and effect?
This is getting weirder than Mahayana!
There can certainly be a lot of talk invested in exploring how khandas function in one who is unbound, but they would function, wouldn't they? The blood flows, the senses perceive and the mind cognizes what is perceived. Unless not only the mind but the physical form too is kammically unbound and one is not only freed from ignorance in the sense of grasping onto the sense of personal self, but of all so-called hindrances and obscuration, ie of a body bound by the laws of kamma and dependent origination, of time, of locality, etc etc.
I've read materials that could support this but is there something like this in Theravada?? (Ok, I recall some Thai monks apparently being able to be in different places at the same time, so something's gone awry with locality there...
Otherwise all that can be said (it seems) is that just because an arahant does not make the error of reifying and identifying with the khandas, doesn't mean it is not useful to denote certain "heaps" of functions as "form", "sensation", etc...
But maybe it is not useful to speculate about arahants...?