"I find this exact subject comes up all the time with these guns."
Yes, it certainly does, and the reason is, really, Smith & Wesson themselves.
They set a series of... expectations... for want of a better word, when people learned of the I frame and the Improved I frame (prior to WW II the letter frame designations were pretty much an in-house thing only, not really known to the outside world).
I guess a lot of people expected to continue the I frame, Improved I frame series for the new models chambering .38 Special. But, with what... Super Improved I frame?
What makes it even worse is the knowledge that the Improved I frame is an enlarged version of the I frame - they're not identical.
It really compounded the confusion that the early Chief's Special guns used Improved I frame grips -- J frame grips won't fit these early guns, at least not well. Then you're getting into the entire walks like a duck, quacks like a duck, it must be a duck.... Well, in this case, it's a platypus, and you really can't blame people for thinking that they have a Chief's Special made on an I frame. But it's not.
At best I'd call it an I/J transitional with characteristics of both frames. But, because it chambers the .38 Special 158-gr. LRN cartridge, which the Improved I frames can't, it's a J frame.
I'll let you know what Rick says when I hear back from him. He's not particularly speedy in his replies.