Does it matter which port is the inlet on a 3-way shower valve body?

[rhw80]

I have a contractor installing a Moen showerhead and hand held (there's no tub) that can't get the diverter to work correctly. Water will come out of the showerhead but not the hand held. The valve body is #12009. Does it matter which port is used as inlet on the valve body? The valve is installed 90 degrees counter clockwise from a T, i.e. what would normally be the bottom of the "T" is to the right as the outlet going to the handheld. The right side of the T faces up to the shower head and the left side of the T faces down to the supply lines from the hot/cold valve.

 

[hj]

If he has the showerhead connected to the inlet, (usually the center bottom opening), it will usually ONLY operate when those two openings are aligned..