Yeah. McDaniel has literally no motivation to tell the truth in this "confession." All he had to do was tell a good enough story so that it can be said that he confessed, that's it. But he wasn't going to (and didn't) confess to anything beyond that.
It seems to me that was the whole point of this plea deal for him: getting a chance to save the tiniest, thinnest shred of his reputation is the one thing he got out of it. Sure, they dropped the child











and burglary charges, but life is life, whether you're convicted on three counts or one. Why would he give up a chance of acquittal (even if it's a vanishingly small one) in exchange for a sentence that's the same as if he were convicted?
This way, McDaniel gets to control the narrative. He was almost certainly going to convicted, but now, instead of a messy trial that would condemn his character forever, and let all his nasty secrets out, he gets to have an official "confession" that depicts his crime in the best remotely conceivable light for him.
Hence the "poor me, yes I am murderer, woefully tortured by my dark, inborn pathology, of which even I am unable to comprehend. I didn't mean to kill her, though! She was my friend! She woke up, and I was caught off guard, in the heat of the moment I don't know what came over me... it just spiralled out of control... I know I can never be forgiven, for my story is so very dark and tragic; I can only wish I hadn't been cursed with this innate twisted neuropathy. p.s.: I didn't do anything sick with the body, I promise, it wasn't like that. I'm just an accidental murderer, not a sicko."