macOS is using "dot on top of the Close button", to indicate both that there are unsaved changes, and that if you tried to close the window, you would get a prompt asking about unsaved changes.
Simpler, more elegant, better integrated solution, consistent across the whole OS.
"Asterisk in the Title Bar" is a very unrefined solution to the problem.
The asterisk (as unsaved indicator) has been there on a lot of Linux programs for a while (the first I remember encountering was GIMP at least a decade ago).
It shows up on the titlebar but more importantly in the window pager/taskbar, which isn't a feature on Mac OS (though to be fair it also doesn't show up on Linux/Windows desktops that are configured to show icons only in the window pager).
Simpler, more elegant, better integrated solution, consistent across the whole OS.
"Asterisk in the Title Bar" is a very unrefined solution to the problem.