Performance distributor gear installation
No, the spark scatter problem
does exist and this is exactly why the metal gears were produced in the first place. Let's not try to rewrite history. I purchased new and used parts to check this out and then measured them carefully so it is not speculation: consistent wear marks on an actual slant six plastic distributor gear that walk up and down the face are not caused by chain lash or cam walk though each of those can also cause spark scatter by a different means.
High aeration levels of oil in an accelerating engine that load and unload a pump driven off of the cam gear can also cause spark scatter.
Building a proper high performance engine is an exercise in a collection of tasks that seek to improve or optimize the system.
Buying a metal distributor gear for $45 Australian does not seem to me like a high dollar, high effort exercise. I am not blaming you in particular -- you agreed with this and attempted to use the correct metal distributor gears in your distributors but they became unavailable under US parts lists.
As for the gears I ordered, I did get one, many years ago. It is still in my "go to the track, spare parts box". I never had a need for it.
But you did try to order more. They were no longer available.
Putting in a totally different DIS system is an option but certainly
is high dollar and high effort. I don't think the withdrawal of metal distributor gears from the US market happened because people switched en masse to DIS. I think it happened because people were unwilling to spend an extra $20 or $30 dollars to buy a quality part.
The manufacturers also responded to this market pressure via the deterioration of the quality of the plastic gear itself. You're not taking this deterioration into account -- the situation with the plastic gear is just getting progressively worse, not staying the same. Remember that I have now compared NOS plastic gears and current gears made over decades and the trend is clear.