The Eidah HeChareidis posken’s that they’re safek Jews, so you have no heter for your selling chometz to them stance.
I admit, I can’t back up what I’m saying any more than YO could when he referenced Rov Ovadia Yosef. <strong>(Modified)</strong>
Millhouse: if you did 23 and Me or some such thing and it didn’t come back Jewish, you would go ahead and eat pork? I don’t care how much sense it makes in your head, we don’t posken by genetic testing.
You guys seem to be assuming that because the stance is more PC, it must be more meikel. The psak that they’re safek Jews is a chashash, not a kulah. Presumably they cannot marry kohanim or mamzerim after geirus. Even if the odds of them being Jewish is 1 in a hundred, it’s worth taking the precaution.