Why are there two different cable-tie points on the module?

They let the incoming cable approach the termination in two different ways. There is a moulded loop at the rear and a projecting strip at the top, so the cable can be restrained according to whether the installation calls for it to leave broadly parallel with the module face or turn through roughly 90 degrees.

It is a small piece of flexibility which becomes rather valuable in a cramped backbox, where forcing every cable to adopt the same route would be an unnecessary contrivance.