True, but in that case it was saving them money by skipping 2 screws, 2 fuse folders, 2 fuses, and 4 extra solder points; plus labor. This individually does not amount to much per game but over 100,000 or so games odes add to the bottom line. So why fix it if its making them money and is rarely a problem. In this case it was costing williams money to keep adding a "useless" switch that could also cause problems. I think there's gotta be a reason to keep it in the design all that time. Too lazy to change does not overrule the bean-counters.

who knows, relatively frequent issues, UL certification, could be anything.

Of course bean counting isn't why the "extra" switch is in there. If it served no purpose the bean counters would have eliminated it. The fact they did not eliminate it points to it having a purpose.

I'm not giving him flak, I'm just being the devils advocate. I am nowhere near an expert on EM's or any era. I have a few but they have not required major work, lucky for me.
But like the OP said skepticism is healthy. He's skeptical of the design. I'm skeptical that 50+ years later he found an issue that no one else ever did. I think the engineers, ops, techs, and later owners would have found this issue, if it was one. If there wasn't one WMS wouldn't have paid to add the extra part and work.

It's been rationalized that "there wasn't the internet" so Williams, or the public, was never informed when these problems occurred in the field. I can agree with the lack of internet, but WMS would have heard from OPS, and this type of fix (undocumented) would have been seen in games that people have now. Has anyone seen this fix applied to a game they acquired, it does not appear so.

The fact this discussion exists is great.