Forgive me, but I can't figure out why any "conflation" would be necessary to explain this very straightforward fact. What am I missing? Himmelsbach has it in his book and in his head. Years later, after the book exists, and after Himmelsbach has repeated the data point and believes it to be true, a suspect is suggested who has that as one of their traits. That seems completely normal. Each suspect has lots of traits, some of which directly correspond to the boilerplate, some of which don't. It's not weird at all that two suspects might share a trait, particularly this many years apart and this many suspects later, and expecially given that now the stains are "out there" as a thing.
If anything, the odd part is that that particular trait showed up that one and only time in the boilerplate, as @olemisscub says. The rest is entirely linear and utterly explainable.
What am I missing?