you should check out modular lowers, hydra and i think viper-A [or vipera] have re thunk the lower into two pieces, result being exchangeable magazine wells to match the upper config.
why would someone actually chop a lower? because its not available, or its a do something winter project to chase off the cabin fever.
if you have a photo example of someone actually doing that on an ar15 magazine well i'd be very interested to see what the hack job looks like