A program for calculating the strength of the guard on random maps in Heroes of Might and Magic III, called H3CalcGuards.

Yes, that makes sense. The AI Value for Djinns and Master Djinns is not significantly different (884 and 942), so with small numbers, they might appear in equal quantities. However, the number of regular Djinns on the map is 8-16 (average 12), while for Master Djinns it's 8-12 (average 10). If the average number in a guard is less than the average number on the map, then that monster cannot be generated. Apparently, the average number of Djinns is slightly less than 12 (rounded to 12), which is why they are not placed. But Master Djinns have approximately the same average, and their minimum average number in a guard is 10 – and they are placed.