I did not even know you could get tapered pegs like that. What I am familiar with is a peg with a common circumference. When we drive the peg (especially if drawbored) the end is "beveled" (for lack of a better word) so as to get through the tenon. Otherwise without the "bevels" the peg just hits the tenon and stops. Pretty fast to fabricate. Get chisel started in peg at the right angle and slam both on a piece of wood, off comes the chip.
