I've found that turning the racking tube down or at least horizontal before I close the fermenter works great. If you have it pointed up to start the tube will fill with sediment. I've had my conical for 7 or 8 years now and by using a trub dump about 3 days into primary and then a long primary I almost never fill the cone with enough sediment to get sucked out through the racking tube even with it pointed straight down.
But to actually answer your question I guess it might, I've never had a problem as long as I have the hard gasket properly seated.