Which is pretty decent evidence that the Bogeyman not a race of Creeper. There are tons of phobophage species out there, just because that one is classically associated with children doesnt make it one of these things.
It matches them in every other way. It preys on children and is undetectable to adults, including wizard adults. The way Harry describes it puts it pretty well in line with the way Maggie talks about the Creepers.
Occam's razor, guys. It's a far simpler explanation that adults simply forget something from their early childhood (and which they can't sense as adults) than that they literally cannot retain information about them.
I mean, you still have Dresden-verse adults remembering what their children say about the "monsters under the bed," and such. Just because they don't
believe it doesn't mean they're incapable of retaining information.
Or are we positing that the enchantment is so subtle and specialized that it can only block information about bogeymen and the like if it's "true" information?
Really, it's not in any way different from
adults who encounter the supernatural and then "forget" it or rationalize it away. "There's no such thing as creepers, that was just a silly thing I believed when I was three, but I know better," is exactly the same as, "That wasn't a ghoul that jumped me and my partner, it was just a big, drunk guy on PCP with a couple of knives."