Your info gets saved when something happens to you. As example you jump into a system, or finish a supercruise, dock, trade, etc. I think "Save and Quit" is just an extra insurance when you want to log out.
Otherwise, if your game crashes it will revert to the most recent autosave. Example I SC towards a station and the game crashes when trying to connect to the stations instance, when I log back in I am in normal frame where I jumped into the system.