That's because Hatcher made a big deal about LSN 1903s and wrote they shouldn't be used. So it became "received truth". Somebody always get s offended when somebody else colours outside the lines.
You see this constantly with loading data. If you mention exceeding loading book or SAAMI maximum for any cartridge, multiple people will post in all caps never to exceed the max, certain death, only fools cross the line by an inch etc. . . .
. . . Unless some magical authority does it. If you point out that Keith loaded the .44 Special to mag levels and why this worked, you hear that he had special magical authority the rest of us lack . . .
. . . or until the rule-breaking is in print. Then it becomes okay to load a headstamped .45-70 case to pressures that would Kb a trapdoor but which a No. 1 will eat for breakfast, because now it's in a book.
True story: a few weeks ago I noticed a low number Springfield sporter in a shop, the tag said "DISPLAY ONLY, DO NOT FIRE". I didn't mention the rifle to the shop owner, but later we had a long conversation on a variety of loading-related subjects. And he told me about a now-dead older mentor who worked for years with Hatcher "back in the day". And that mentor who'd worked with Hatcher unhesitatingly shot LN Springfields, said he didn't bat an eye over them.
I didn't even ask the LGS his reason for the doom-and-gloom tag on the Springfield. I know the answer. He's got nothing to gain by trying to educate or argue with customers.
Near as I can tell Rolling Blocks Kb, Swedes Kb, Krags crack lugs, nobody cares what their hardness or carbon content is compared to what it was supposed to be, and nobody questions them because those aren't official questions.