A gunsmith I know Ed with just a few years more experience than yours disagrees with that. He says that any steel made after WWII is adequate to handle steel shot. What matters is precisely what Homeless Joe is reported to have said in Jagermeister's post above. The early steel shot shells were dramatically inferior to those produced today, from waterproofing to shot cups/buffers, etc. The size of shot also makes a major difference, i.e., no shot larger than 4s through modified and no steel shot period through full chokes, etc, etc. I have a Stevens Model 311 that my Dad bought for me on my 13th birthday in February of 1962, choked modified and IC. I have shot ducks with steel 4s with it several times with absolutely no damage done to the bore or the choke/muzzle end. I have shot either Remington or Winchester steel loads.
