it's the biggest pile of twaddle i was ever told
Many locks use brass Levers, Pins or Wafers, so steel/alloy keys can & will cause wear to these parts over time
Take a look at quality of the cut your equipment makes, are the sides of the peaks & the base of the valleys smooth, if these are jagged or have a filed appearence then you cutters are blunt or the blanks are being cut through too fast
Steel keys cut in this poor quality fashion will wear the internals of a lock, because they have a file/saw like action on the brass part within the lock