From a linguistic standpoint, restrictive vs. non-restrictive is determined by whether the modifier is semantically required to determine the referent or not. If it is “or not”, then it is considered to be doing something other than the expected semantic function. I could see that English grammar books would be pretty pedantic about the matter, but linguists ought to know better. This processing hierarchy was a core contribution of my doctoral research. I do not have a ready source to provide you regarding non-restrictive reflexives. I agree with you that the appositives in your examples are non-restrictive. I argue that this fact is what opens them up to interpretations of accomplishing some pragmatic function. If they were semantically required there would be no room for making such an inference, its presence would be explained by the semantic need.

why aren’t reflexive pronouns used as intensifiers treated as
nonrestrictive elements?

for example…

I, who am myself, am myself. the adjective clause is obviously
nonrestrictive

I, Bob, am myself. the appositive is obviously nonrestrictive.

I myself am myself. every source i’ve looked at shows examples which
treat the first myself as restrictive (i.e., it isn’t enclosed with
commas)–but i can’t find a rule about why a reflexive intensifier is
treated restrictively–

thoughts?

James