That is rather... oblique.
I think it is a stretch to say that a fallen was certainly involved when Michael killed Sithorax, and Michael was still exhibiting some pretty strong patronage (that is, he seemed to be on the clock) when he pulled some pretty interesting tricks without the sword in GP.
Also, Murph was undeniably on the clock as a knight when an archangel sock puppeted her at Chicken Pizza in Changes, and I didn't see any fallen around then either.
Point being, I doubt fallen involvement is absolutely necessary for a knight to be on the clock. Of course I also doubt I may sway you on the matter.
the dragon and reds count as 'general supernatural evil' so i shouldnt limit it to just fallen, perhaps i was unclear. Im basing this partly on JIm's comments about angels, and the things uriel said. that being so, ureil is kinda sneaky about bending the rules
but somehow I still suspect lasciel made harry trip off that ladder
the whole make him commit suicide thing isnt effective if the situtaion isnt hopeless, and it explains why snaya showed up then quite nicely-
the general idea is that much like summer opposes winter, the light opposes the dark- but as they fight on a much larger scale they also have more strignent rules.
in order to preservce free will, the angels pretty much have to wait until after the devils get involved
and whose to say the devils werent involve dsomehow in the red court? or sirothrax? I dont know of any rules saying the bad guys have to just use the fallen- uriel uses harry all the time, just because he's a good man.