alt Hacker NewsReddit has a toggle in its settings to disable it. X, too, I think.
Personally, I wish iOS didn't even facilitate this.
edit: to be clear, I don't think iOS should notify the app at all. The app could register areas as "invisible to screenshots" perhaps - I'm torn on that functionality.
That's what bluesky is doing in this case. It is showing the button on an area that is "invisible to screenshots", and the butterfly is behind it, so it shows through when a screenshot is taken