Henrique de Moraes Holschuh:
Note that the ideal implementation would be to inherit the umask [...]
Actually, the ideal implementation from the GNOME point of view would be for these programs to pass the umask from the client process to the server, just like they pass open file handles, the working directory, environment variables (including DISPLAY), and the arguments vector.
* https://github.com/GNOME/gnome-terminal/blob/52f32f962a5ed34f8c31042f2f8276dc1710cc99/src/terminal.c#L317
* https://github.com/GNOME/glib/blob/b51a0e7c63313ecfc0c6bbb9f2a8d99f193e51ea/gio/gapplication.c#L923