Yes, we know that; any turrets can't find targets if they are beyond the 70% of the turret range, when the range is equal/greater than 100 tiles, but after they are triggered, they can shot at the full range.
We wanted design an new artillery turret for the end game, this is the better solution that we found. Unfortunatelly Factorio have an infinity amount of limitations in the modding world, and sometime we have to take compromises. I'm sorry, this can't be fixed and we will not change this in future.