Does it matter?
I mean.. Really?
I was born Asexual.
Do I go on and on about it?
No. But that is an imperfect parallel, to the point of being misleading.
Sexuality develops spontaneously, and there is little in the way of social pressure for you to have it.
Theism, by contrast, is sociallly construed, with very few exceptions and maybe not even that. While Atheism - and that is mine and outhouse's point which you all seem to reject - is pretty much a default state.
Implicit Athiesm is a stupid concept when concerning infants, Because if you can't form an opinion, Then you're not a true Athiest until you are capable of deciding that you are.
Only if you take as a given that atheism must be informed to be meaningful.
I see no reason other than peer pressure to even consider such a premise, personally.