Buried in the middle of it, there's a point where the North American says their own source is the advance proofs of the confession Holmes' own hand (presumably the one that was published in the Inquirer, which they studiously avoid mentioning). Through most of the article, they subtly imply that the confession was written for THEM.
My first inclination was to think that they got a look at the proofs and tried to reconstruct it from memory - this certainly seems to be the case in the parts about turning into the devil, which are also in the Inquirer, though in different words. However, none of Holmes' direct quotes in the article actually appear verbatim in the full version, and a couple of sections are unlike anything that occurred in the confession at all, making me wonder if they just made it up altogether.
This is all probably going to boil down to whether The North American was a respectable paper of more of a tabloid in 1896. Most of the other articles that I can see in the margins of the scan seem respectable enough, but most of this article is pretty much "pot boiler" writing, re-stating a few main themes and concepts over and over to stretch what little info they had to go on to cover their full front page.
Many regional papers printed excerpts from the North American, including the portion about Holmes mutilating his son (which does not appear in the full version). Since every regional paper demurely refrained from including all of the details of that part of the story, I had thought that their source paper might have the full version, but it doesn't appear to. Since the scan of that portion of the paper at the Free Library was unreadable, I've filled in the blanks using an excerpt of it published in the Sydney Morning Herald.
My full transcription of the article is below - thanks for Peter Stone Brown of Philadelphia for digging it up at the Philadelphia Free Library!
PHILADELPHIA NORTH AMERICAN
Saturday, April 11, 1896. Eight Pages. One cent.
HOLMES' CONFESSION.
The Story of the Most Horrible Murderer Ever Known in the Annals of Crime
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STAMPED BY SATAN HIMSELF
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The Multi-Murderer Feels That He Is Gradually Turning Face and All Into a Demon
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DISFIGURED HIS OWN FLESH AND BLOOD
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The Man Now Sitting In the Shadow of the Gallows Tells How He Took His Little Son into a Barn and There Committed the Most Horrible of Crimes - "I Was Born With the Devil In Me" - A Fearful Narration of the Taking of Twenty-Seven Lives - His One Regret."
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The Story of the Most Horrible Murderer Ever Known in the Annals of Crime
--
STAMPED BY SATAN HIMSELF
--
The Multi-Murderer Feels That He Is Gradually Turning Face and All Into a Demon
--
DISFIGURED HIS OWN FLESH AND BLOOD
--
The Man Now Sitting In the Shadow of the Gallows Tells How He Took His Little Son into a Barn and There Committed the Most Horrible of Crimes - "I Was Born With the Devil In Me" - A Fearful Narration of the Taking of Twenty-Seven Lives - His One Regret."
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(click to see the full transcription of the article)