It makes the task of black far too difficult in comparison to white. There is no balance anymore. Why should a higher-rated player want to play black when a lower-rated player can so easily force a draw?
It is a shame when a serious game is corrupted by such an easy way out for white. Compare with chess, where perpetual check is hard-fought for.
In a good game you have to EARN a draw (if allowed at all).
The castle-building draw in Tablut, where black can only win when white is running out of movements is enough possibility for white to earn a draw. [By the way, even with lin.rule nr 11 castle building near the edge is still possible].