Now there's a correlation I hadn't thought to examine.
Look at what Romans 11:25 is actually saying will happen: as long as there are Jews around, they will not see the divinity of Jesus and will argue against it. Well of course this was going to happen. In practical terms, Jesus didn't do what they expected the Messiah to (standing up to the Romans would have been a good start), and it was the Jews whose representatives supposedly got the guy killed. To acknowledge Jesus as Lord is downright un-Jewish.
I refer you again to my piece on prophecies, and suggest #1. High Probability of Success as a far more likely explanation for the accuracy of this prediction. In other words, it was a no-brainer.
Meanwhile, the cultural background of these atheists is irrelevant to the soundness of their arguments and counter-arguments. If you want to call them Jewish atheists, go ahead, but it doesn't invalidate a thing they've said or written.
One atheist writer who certainly doesn't fit the supposed pattern is Ayaan Hirsi Ali, a Somalian ex-Muslim. Possible other exceptions are Dan Barker, Richard Dawkins and Brian Sapient as you say, plus Daniel Dennett, James Randi, Michael Shermer and Victor Stenger. I haven't got a single Jewish ancestor as far as I know.
I find your defenition of a Jew interesting. It's in line with that of the many religious Jews who essentially declare Judaism hereditary. By this logic not only is it impossible to stop being a Jew (from your list, only Hitchens self-identifies as a secular Jew), but one is born a Jew. Thus you needed to call yourself a gentile as well as a Christian, to emphasise your lack of Jewish ancestry.
Importantly, for the prophecy to even be accurate, the above definition must be the case. Do religious Jews (or does anyone else) have the right to label those who would otherwise be known as ex-Jews?