If you're calculating mate #s based on your own variant chess laws instead
of the orthodox ones, you should have stated that up front.
And if your variant laws include removing the 50-move draw and making
repetition illegal instead of a draw, then the numbers you are calculating
are likely much closer to helpmate numbers than forced mate numbers.
Eventually, ALL non-mate positions will be exhausted, and black will be
forced to collude in his own checkmate by process of elimination.