In addition to being a poor way to judge if the ball is seated, it is just a poor way to seat the ball in general, for a number of other reasons. Firstly, with a soft lead ball, bouncing the rod can deform the ball. More importantly, accuracy wise, consistent pressure when seating the ball is one of the many variables in accuracy, according to several world class LRML shooters. Over-compressing the powder can cause higher pressures in the chamber. Oh, all of the above refers to actual black powder, now that I think about it. I don't know sh#t about 777....
As always, YMMV