Even after truly repenting for and confessing the loss of virginity, does the church still need to know about it before marriage, although in God's eyes this sin is forgiven and forgotten?
Although the sin is forgiven, one has to deal with its consequences. A girl who gets pregnant and have a child out of wedlock; will not get rid of the child nor deny his presence because she has repented. Likewise, loss of virginity has its consequences: it can be a reason for annulment of marriage later on even after repentance and confession. That is why the church has to know before hand.