Loss of one hydrulic system is hardly an emergency, the return is just a wise thing to do
Yeah your right to a point......however the left system on the 757 is the heavy system, landing gear, nose steering, flaps/slats, Alternate brakes..the various left system powered flight controls, and of course the left reverser. As a consquence yes the aircraft is flyable and safe....but it is an emergency in every sense of the word
About the only thing thats gonna work as advertised are the normal brakes.