Keith was writing of the use of a cap and ball revolver as a working revolver. He felt the use of lubed wads improved utility as in contributed to a reduction in fouling/leading.

I've played with >30 1860s (originals and repros) in a Ransom Rest, tweaking one factor at a time and seeing what the effect was. Testing from temps of -25C to 46C, I've not seen any significant effect of tallow-lubed wads on velocity. (I suspect this is due at least in part to seating the ball to the same depth with and without wads: the charge in the wad loads are compressed more than the loads without wads.) Groups were fairly consistent, from the first cylinder to the 8th.

With the right lube smeared over the seated ball, you can usually get similar results. The lube is messy, and shot-to-shot consistency can be an issue. It is also a pain to holster-carry a revolver loaded in this manner. I think Keith--and the folks he learned from--were trying to avoid this.

(Wads dipped in beeswax resulted in a slight--appx 25 fps--increase in velocity but less-consistent grouping. Usually by the 5th cylinder or so, fouling became an issue.)

Curiously, I've never had an accidental chain fire when using balls that were oversized for the chamber, even when shot without lube (and I've fired hundreds of shots this way). I've been able to experimentally re-create chain fires by leaving caps off a loaded chamber, but even then it doesn't happen every time.

If you really get into shooting a C&B revolver, there are all kinds of tricks and tuning you can do to improve or optimize performance for your purposes. In that way it is like any other pistol.