Okay, let's talk about that "Adventure of the Mazarin Stone" weirdness.
Dr. Watson is writing it, but pretending it's not him writing it. He's still the guy whose point of view tells the story, "It was pleasant for Dr. Watson to find himself once more . . . etc," so we know it's him. But it's almost like he's embarrassed to be putting this one to paper.
Sherlock Holmes is also using the very same wax-dummy-to-bait-a-sniper trick he used in "The Adventure of the Empty House," the case where he caught Colonel Sebastian Moran in an exciting ambush during an assassination attempt. Colonel Sebastian Moran, who was a tiger hunter that favored air-guns for his city work. And in "Mazarin Stone," we find "Count Negretto Sylvius," a lion hunter who favors air-guns for his city work . . . to potentially shoot the same Sherlock wax dummy that Moran did.
Now, most folks pondering this situation just see "Mazarin Stone" as a cheap knock-off stealing pieces of "Empty House" for a more theatrical piece that may or may not have been created by Watson's literary agent. It's a very believable thesis. But like Sherlock Holmes, we must always consider other possible options before settling on one particular theory as fact. So what might another option be?
Well, let us suppose for a second that we've had these two tales reversed all along.
What if the "Mazarin Stone" gambit was actually the way Sherlock Holmes caught Colonel Sebastian Moran at the end of his hiatus, and that the dramatic "laying in wait for a murderous sniper" part was Watson's literary agent going, "You can't bring Sherlock Holmes back from the dead by having him catch a criminal so stupid he can't tell a real person from a wax dummy, when the person is so close they can snatch a jewel from his hand!"
I mean, even Sherlock Holmes had to be a little embarrassed, having avoided London for so long, thinking Moriarty's second in command was a capable second, with a cunning mind all his own, when Moran's lights were only reflections of Moriarty's, on a shiny Nigel Bruce of crime.
With his glorious writing comeback in "The Adventure of the Empty House" half based on fraud, Watson would have been haunted by that guilty secret. So haunted that years after he put his Holmes chronicles to bed with "His Last Bow," Watson wanted to publish the true facts of the Moran capture to ease his conscience, even though "His Last Bow" was supposed to be the end of it. Between his literary agent and The Strand Magazine, that spark was fanned into the flame of an entirely new set of stories, The Casebook of Sherlock Holmes, and the true Moran capture tale disguised with some false details . . . details that still made Watson feel so guilty he wouldn't allow the tale to be published in the first person, something to leave a clue for future readers as to his true feelings on the case.
Yes, the previous tale, "His Last Bow," from four years earlier, was in the third person as well, but it was a tale whose telling required that mode -- Watson wasn't present until the last. But "Mazarin Stone" is, in its shape, a normal Watsonian sort of tale. Except for the "It was pleasant for Dr. Watson to find himself once more in the untidy room of the first floor in Baker Street," which sounds a lot like his return their after the Great Hiatus, doesn't it?
It is said that a group of pandas is called "an embarrassment of pandas." If this theory proves correct and "The Adventure of the Mazarin Stone" turns out to be the actual record of the capture of Sebastian Moran, perhaps we'll want to borrow that term to refer to our Moran/Sylvius grouping of Moriarty lieutenants.
An embarrassment of Morans . . . for a lot of folks.