Well, I also tend to open the editor via click on the project and closing the launcher before it can fully open.
Although what I found out (by accident), when I wasnt connected to the internet when I launched, I choose “go offline”.
And since then, even I am connected to the internet, the launcher starts and asks for my credentials. So I have all the time in the world to close it.
Mostly I see those big launcher “updates” when new stuff is being added to the market place or learning tab…