Footrest mount question

I have a '74 Roadster. The parts list shows the left footrest is mounted to the support plate (Z plate) with 3 studs and nuts. The right footrest is mounted with 2 studs & nuts, and a bolt and nut. Why is a bolt used rather than a 3rd stud and nut? Is there any reason why a third stud can not be used?
Thanks, Jim

The zenor diode mounts to the back side of the Z plate with a nut. If you've replaced the zenor with a solid state regulator then you can use a stud and nut for a balanced look

Just a suggestion to keep your primary cover from getting dinged.
Put the nut on the peg before you screw it into the footrest holder.
Tighten the nut against the holder and cut off the excess threads sticking out.
This will give more clearance between the footrest and primary cover and help to keep it from being marked if the footrest is bumped hard or a minor tip over.

I believe that the bolt is used to secure the red double ground wire that has a ring terminal to the inside of the Z plate with a nut.
This ground connection couples with the Zener diode heat sink.

I have often wondered if it's good practice to have an earth ring between the zenor diode and the Z plate
After all the Z plate is the heat sink did they come from the factory fitted this way?

thanks everyone. I will be going with a solid state rectifier. Sooo I will use a stud instead of a bolt.