I'm curious about the last paragraph relating to Signal. How, exactly, have Brave managed this without also blocking screenshots? Is there a flag Signal missed?
 replies(3): 
1. "Browser" does not mean "web browser": many kinds of applications can be considered a browser.
2. Even if you identify "browser" with "web browser": Electron apps are basically (web) browsers (though not fully functional ones). Nobody claimed said for a software to be in the "browser" category, it has to be a fully functional web browser.