Hi basically i work on guitars and i have always known that frets need to be crowned for the best set up and playability, but i heard somthing today which is new to me and am wondering if any1 has heard about this before,

I had someone to come to me with a issue with there fender, they had the frets changed and the nut adjusted but there getting a twang sound from certain strings, They told me they purposely having there frets flattened and uncrowned , Has Anyone ever heard of having the frets de crowned for any reason?