I was pondering how one of these shallow divots might be used in a real world situation. I wonder if rather than a carry area for the lube for general everyday purposes, if the hole was set for a speedy followup shot in a known emergency situation. I do not know the time period these grease holes are used but perhaps putting the rifle in historical context might help answer the question.
I had read an article in Precision Shooting magazine that spoke of a man carrying a ball in his cheek in an attack situation. He was running after an enemy and powdered the rifle and put the unpatched ball into the rifle and fired. Not greatly accurate, but surely minute of enemy.
Perhaps the "grease hole" was a variation on that type of a theme. Put grease into the hole. Quick load is to grab a ball scoop the grease gob up with the ball and shove it into the barrel. I might go as far as to say I could find the grease in a small divot faster than somewhere else.
One could reach for ball and bring it right past the right side of the rifle on the way to the bore...
This is probably not the best place for this type of discussion, but I will leave that to our administrator.