cutting shank on faucet

I am installing a price pfister roman tub faucet the direction call for cutting the shank and only leaving 1/16" above the anchor. Can you tell me why this is needed. Since the spout is tall enough that it goes all the way in the way it is. Thanks, Sharon

 

cutting shank

The need for cutting the shank is dependant on the thickess of the deck or tub that the filler is being mounted on,lay-out how the valve is to be installed and see if the shank interferes with hook-up under tub to determine if shank needs cut,if you must cut,(hacksaw,sawzall)use a file to smooth this cut edge as not to damage an O-ring in the filler spout