The Amish are not a monolith. You’d have to look into the various groups to get your answer,and it won’t apply to all of them. And some do use power on the grid, while others like the Old Order Amish don’t use it apart from maybe some battery operated lights for night work or portable fans. I doubt an internal grid is used in most if not all places considering that, while many do not mind use of electricity, it’s still used in relative moderation.
To your point of chemical changes vitamin D2 is produced by light exposure. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6213178/ It specifically refers to UV light, but the chemical changes are due to the light itself, not a metabolic process.
If you never shave, you probably shouldn’t go out doing it the first time. It’s a nudist resort, not a porn shoot. Probably be a mix of both. Course I suppose it depends on the specific place. But I’ve never met a nudist, that I know of any way, that bothered to shave.
It’s from a song https://youtu.be/8-r-V0uK4u0