But these are forums, and vintage bikes. Not businesses needing to get running. A person does not get into something over 40 years old and onto forums because they will be late for work if they dont, it is about experience of ownership.
In this case, the OP's charging system was working, but not at full output. If he had reported a .5 V drop at the black regulator terminal, that would mean the fuse block, ignition switch, and the connections between them are not the issue, and I would have moved on to the next logical step. Since his readings were higher, it means there is no point looking elsewhere until that issue has been resolved.
This is what was missing initially in the post. Multiple test suggestions were given. Some explained why to check it. "A common charging issue on these bikes is because the signal to the regulator can get corroded resulting in the regulator discharging too much. Test voltage on X to Y, and if above 0.5v, then there is corrosion somewhere. Follow the wires from X to Y. Recommend cleaning regardless"
Same info, but clearer and more understandable. But instead, there were multiple easy checks that are general across more bikes, and one more specific one without reasons. Just "Check this" and that meant our member who sounds like has a fantastic barn find went the understandable routes first and was berated over that decision. That was the start of the tension. The words were a reply to a tense situation already created. Then after, the solution was locked in a lead by the hand answer. The way info was given meant our owner here really had no choice but to be handheld through unless went and looked for answer elsewhere. In which case, it would make any attempt at help on your end have no value.
Made the comment about not being "modern?" In a way... Probably true. Internet and in general the ways of the world on the whole have changed. Sometimes the old ways are best left in the past. As the British motorcycling industry how stubborness worked for them?
The worst part is again, You have very valuable knowledge and experience, but if the way it is shared drives people off, it will just be lost. Not sharing the logic of the problem solving makes for terrible mechanics. It is actually a serious issue. Modern mechanics are not taught to work things out logically. They are trained like you shared the info. Just do ABC, then fix D without any whys. Result is mechanics can only fix D, and not determine it is E.
Great example is my car. Had an oil leak. Not old car. Usually I can fix it myself, but couldnt get it in the garage to do so. Like a 1000 dollar repair. Oil cooler was leaking, so booked in and got parts. The dealer pissed me off so I just bought the parts to do later. Turns out that it wasnt the expensive oil cooler, but instead just an Oring which was pretty easy to determine. But the mechanics are not trained that. Working on stuff isnt taught as a skilled trade anymore but is quick mass production commercial education which doesnt work for diagnosing old vehicles.
Reasoning needs to be shared. Help the peeps to learn how to wrench on by explaining what and why they are doing something. We dont live forever and if we dont pass it on, the information we know wont last either.