My gut tells me that you would certainly lose a few grains of powder using a tallow soaked felt wad - not just in space used up but in unburnt granules getting thrust into the underside of the wad. That must be happening to some extent in my opinion.
It works, sure, but unless you recover a blown wad to inspect one wouldn’t know for sure.

As to chain firing, I suppose the smear of lube over the ball is preventative but a ball skived at the cylinder mouth is a pretty good seal in itself - that is if the mouth of the chamber isn’t tighter than the body of the chamber. I’ve heard of that but haven’t measured any of my revolvers for that.