Well the most common way the clown would feed is simply...poop...cause they all do and the nem will filter feed.
If you are lucky and your clown/s are good hosts, they will actually spit food into the nem, and I've had some clowns that did this at every feeding before even feeding for themselves.
Fautin and Allen may not have observed this in the wild, but who's to say the clowns they observed were comfortable w/ their presence enough to act naturally( Though I still greatly respect them and their research, I just would not assume they are 100% correct on everything)
Really though, the reason people will say you do not have to spot feed is because light is their main source of energy, w/ good lighting a healthy nem does not require spot feeding at all.