D. Todd Christofferson explains baptisms for the dead are not considered binding, no name is added to the membership rolls of the church.
D. Todd Christofferson, "Religious Freedom Allows Both Mormons and Jews to Honor Their Ancestors," LDS Newsroom, November 10, 2008, accessed March 2, 2021
Temple rites are not considered binding on the departed soul. A temple baptism is an offering to deceased ancestors who were not members of the Church when they were alive. Mormons believe that even those who have died still think, act, learn, and make decisions in the hereafter. Temple baptisms are therefore free offerings that our departed ancestors can choose to accept or reject as a blessing offered them. Because the result of a proxy baptism is not binding on the recipient, no name is added to the membership rolls of the Church. There is no change in the religion or heritage of the recipient or of the recipient's descendants. There is no possible way of knowing whether that offering has been accepted or rejected.