Anamorphic Prism vs Spherical lens question

I apologise if this seems an overly simple question, I see alot of expert opinion on this forum and I dont mean to waste anyone's time. I have been designing systems based around Anamorphic projection for a little while now but have recently be told by one of my suppliers of high end screens that curved screens are for spherical lenses because they get pincushioning whereas prism lenses are for flat screens. This sounds odd to me, I had always thought that the pincushion was directly related to your throw distance - not ur lens type.