From the KDisplayManager code :

// This only tells KDM to not auto-re-login upon session crash
void
KDisplayManager::setLock(bool on)
{
    if (DMType == NewKDM || DMType == OldKDM)
        exec(on ? "lock\n" : "unlock\n");
}

Given we no longer have kdm in Plasma 5. This hardly makes sense.

REVIEW: 125837