That’s actually how the jet really works. It would be very deadly to immediately jump onto the active leg considering most times when departing an airfield, you are under tower control and cannot invoke autopilot under 400’, many times you must be clear of immediate control tower space and are still under tower and approach control for manual changes to your flight plan until you can join the first leg.
The reality is how the Autopilot and GPS integration worked prior to AAU1 taught so many sim pilots bad habits because NAV immediately took over.