Slant Polarisation RF plumping

Hi,
Does the +45/-45 antenna ports for slant polarisation need seperate inputs from radio modules? Our vendor supplied us with GSM radio module which has only one output port and a single feeder is run to the tower and split using a splitter to provide input to +45 and -45 antenna ports. Is this normal RF plumbing ? Is there any reason not having 2 seperate output ports from the Radio Modules?