I have no idea what their line of reason was to make a left homing machine.
Unless it was to make it easier to manufacture. The left homers seem to be a simple spring loaded system to pull the needle to the left unless it's moved to the ZZ position. But, I do have one that is a left homer when the straight stitch needle plate is installed, and can also be set to center position homing when the ZZ plate is installed.
I don't "think" Singer ever made a left homing machine. I've never seen or read of one or heard of anyone mentioning one.
Joe