Patched ball or bullet will push it down if it sticks.
But if too much of it sticks because the barrel is long or the powder charge is small, it doesn't freely accumulate within the powder chamber to create the fullest ignition [maybe?]. Using a drop tube is how those chunk gun competitors often do it, and they're supposed to be real sticklers for accuracy.
It's probably because I use extra lube in my patches and while most of the excess gets squeezed out at the muzzle, the bore still gets pretty lubed up. Since I don't usually swab at the range, shooting lighter loads helps me to shoot longer by keeping the fouling soft.
So that's why I'd like to try out using a powder drop tube someday. It certainly can't hurt and should only help. Maybe it would even help to promote a little powder conservation by maximizing propellant efficiency.
We should all learn a tip or two from the pro's, right?