Can't be added to the draw by chess rules (or else some rare positions promoting into a KNNK mate will be pruned before the mate is discovered).
So it must be in eval. But how to do it w/o slowdown. Currently escapes the scaling rule, due to the material diff < R condition. Either make this condition more complicated (slowdown), or work towards a proper solution involving material keys and a material hash table. Could be beneficial done with material imbalance.