I think you're overfitting to the average here with your expectations. Especially basing that on the experience level of people who would sign up for help learning how to use Windows products. And even then, the ones learning about copy/paste for the first time will likely make more noise about it then those waiting to see if you'll teach them something new or any that ended up in your training because their work made them or something.

While the majority might lack familiarity, the 40 - 80 age range includes tons of people that have been working with computers (windows or otherwise) since before Windows was even a thing, including many who worked on Windows and/or developed applications for it. Experience will range from not knowing what windows is, knowing it's the OS but not knowing what an OS is, to understanding what goes on in the kernel at a high level of detail.

There's a lot of people on Windows just because of inertia and Linux can handle a lot of the use cases. It makes perfect sense to me that someone, once they've seen that things aren't so scary and different on the other side of the fence, would wonder out loud about why they thought their inertia was so strong.

Your skepticism is more baffling to me than that.