Dumb question: Why is this behavior desired? If I take a screenshot I want an exact record of what is currently displayed. I don’t presume to be a normal user but am super curious about the “other side”.

I’ve run into a related behavior on iOS where I really dig some color palette while viewing in inverse colors and want to take a screenshot to capture it. The screenshot is “helpfully” stored as not-inverted color thereby stymying my efforts.

It prevents the generation of consistent screenshots and looks somewhat unprofessional. It's the same reason why product marketing shots don't have clutter on the desktop or a bunch of random applications running in the background.

No, but sometimes it seems to hide what is behind the translucency so as not to pollute the screenshot. Other times it does not seem to do this. I don't know the pattern or rationale.