A DC penalty will only be applied if the game was drawn.
The reason for this (mainly) is to prevent a potential 35 ELO loss if someone disconnects after level 20 (loss + DC penalty). This means you can either draw the game and report the leaver, or you can simply play the game out. Please note that nothing about !drawing has changed (mandatory for leavers pre 20, optional for leavers after 20).