No I have a similar setup. Hopper above a Dust Funnel and a chest beneath. Takes several seconds (4 is a good estimate) till 72 of theses µ piles are processed.
Even when you hand-feed it. I remember feeding all the sluice-juice-piles from the dryer into it. had to wait a few seconds between every stack.
seems like the funnel takes around 50 Milliseconds to process a single "thing". No matter if its a 1/9 or 1/72