I don’t believe that is accurate at all. Absolution is of God and the Church. Turning one’s self in to authorities is relative to many other circumstances. The Penance is but one.
When would a confession be invalid? When the penitent is not a baptized person; then the penitent is under an excommunication the lifting of which is reserved to the Bishop or the Apostolic See; when the penitent lacks awareness of the gravity of a sin; when he does not express remorse, or an intention of amendment.
"To acknowledge ones sins to recognise one as being a sinner, capable of sin and inclined to commit sin, is the essential first step in returning to God" (Pope John Paul II, Reconciliatio et Penitentia, (1984), n.13). Were it not possible to withhold absolution the very integrity of the act of Christian conversion would be undermined.
"God pardons nothing to those who pardon themselves everything," declared that saintly confessor, the Curé of Ars. Purporting to absolve an unrepentant penitent brings no one to this realisation. It will be a rare case, but when a person confesses a felony, requiring him to go to the police before absolution may be the only way to ascertain that he is actually repentant.