Grohe Grohsafe Pressure Balance Valve

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.

valve

Not sure about this valve, but usual reason is that you might tend to use THAT on/off valve instead of the one in the valve, thus subjecting portions of the valve to unusual pressures, and possibly creating back flow or crossover problems in the piping system.

Thanks for the fast reply. That makes sense to me. I guess that I will need to make sure that the water is always shut off at the main valve after the shower is used.

Any other ideas or advice??