I'll also start this with I have stayed out and should stay out of this discussion but here goes.
I agree with handejector in that there is no need to over complicate things. This hobby shouldn't turn into a legal debate. That takes the fun out of things. I'll let the lawyers who make a living making black and white look grey do that. ( not pointed at my Cajun brother , you know I love you man.)
There is nothing wrong with general information, rules of thumb, etc. That's what helps us when we are at gun shows, face to face sales, etc., to keep us in the right general direction.
I really don't want to get as technical as saying that a model 45 isn't a post office gun because it never went to the USPS , or that's not Coke bottles because it never actually was filled with a beverage.
I know I'm going to a little extreme here but I'm just making a point. Let's go with what we know. It's highly unlikely we will ever encounter the prototype guns or the SA gun. So I'm fine with calling a 35 -39 357 a RM and a 1940 357 a NRM.
If it had a REG number I'm ok with calling it a Registered Magnum because it could be registered , regardless of whether the original owner did so or not. The shovel I bought at Tractor Supply is still a shovel whether or not I've used it to dig yet.
If everybody wants to call Mohammed Ali , Mohammed Ali , I'll call him that, even though I know his momma named him Cassius Clay.