I hope that the illustration was using some "artistic license" as to the size of that front bead?

My take is that the principle would be the same irrespective of the relative size of the front bead.
I do have to note that in the past I have had a couple of vintage/antique English express rifles that have had very fine front beads, likely filed down to a tiny point. I'd guess the owner/shooter had really sharp vision and was after small targets at distance?
- Mike