Rob, for those familiar with the rebarrelled South African Magazine Lee Enfields (Long Lees), you ask a very relevant question!
Some time back the completely flat uncrowned muzzles on my SMLE B.S.A. replacement barrels also aroused my curiosity. I have three such rifles and these muzzles suggested to me that their barrels may have been shortened.
I consequently stripped down two of them to investigate. There is now no doubt in my mind that their B.S.A. commercial barrels were of original S.M.L.E. configuration and have never been shortened or altered in any way.
I also note that the replacement B.S.A. commercial barrels on my South African military MLEs have flat uncrowned muzzles. Was this a characteristic of B.S.A. commercials??