Indeed the use of a greater flap setting will decrease the landing distance by permitting lower approach speeds, greater drag and a steeper angle of descent without increasing the airspeed.
Also not all the aircraft have the same flap configuration. Some just deploy a maximum of 30deg, others can go as far a 42deg or 50deg. In some Boeing jetliners the use of maximum flaps it is not allowed for normal operations, some even have a placard or sticker reminding the crew this condition, to be used only in extreme circumstances such in an evacuation (to help the passengers slide down when escaping from the wings exits).
Also, some Flying Manuals for some aicrafts dictate the need to partially retract the flaps at touchdown to sink the airplane, decrease lift (and with the help of spoilers) increase the braking action and effect of the wheels. In the 727 the normal flap setting for landing is 30deg, immediately after touching down the flap leveler is set up to 25deg.
I have no idea why they used 40deg and no thrust reverses, each pilot after assessing the particular situation has to actuate according to it.
Hope it is useful
There are no stupid questions... just stupid people!