I just got done installing this valve in a new shower I built. Based on what I was told (and sold) at the plumbing supply, I installed a diverter for a hand shower on the output of this valve. Now (too late), I am reading the instructions and it says not to install a shut-off on the output leg of the valve. I am worried that I have effectively done that if I use a hand shower with an on/off function.

What is the reason for not having a shut-off on the output of the valve?

Thanks for your help.