I think it would be best to let it all settle, as well. Remember that there is a lot of suspended break and hop material in the whirlpool, and it simply settles when it hits a pocket of slowly moving liquid (i.e. the center). It isn't actually 'pushed' there by a pressure gradient. Regardless, the moving liquid at the outside of the kettle is moving fastest and will actually have the highest levels of suspended sediment until everything has finally settled, so it probably won't work to siphon while the whirlpool is still moving.