Blender - UV unwrap issue

I’m trying to UVunwrap a simple cylinder but I’m getting strange results. The initial projection gives me a stretching I don’t understand.
I made a 2-minute explainer video with audio narration to demonstrate this issue. Any help you can give me would be appreciated.

video link: https://youtu.be/nWkkA5DoICM

Thanks

I don’t get those results myself when tackling a similar mesh. No matter how thin it gets, the unwrap gives me something I expect to see. Could you upload the model somewhere so we could take a look? If for some reason you don’t want to share it publicly, you could send a link via PM.

Have you applied the scale to the object? UV unwrap, like many functions, deals with the base mesh, before any scaling is applied.