The law doesn't care about biology, the law cares about legal paperwork.
Whoever’s name is on the BC for 0bama as his father is his “legal” father. No DNA relationship required.
Just ask a guy who found out that “his” children that he has been paying child support have no DNA relationship to him - the law cares not, he is still “legally” the father of those children.
That may be true for child support payments. It is not true, however, for citizenship claims. There must be a blood relationship in order to claim U.S. citizenship. See the U.S. Department of State Foreign Affairs manual for details.
Sure it makes a difference. He’ll be exposed as the sordid liar that he is.