I think its just down to the fact they took a while to get it going. they promised stuff early on and didn't deliver for a while.
But I think it was down to training etc the same as HIMARS taking time to get to the field.
It's because Olaf Scholz is fucking useless and the military has had to go around him to donate stuff. But they have donated loads, mostly by releasing German manufactured equipment sold to other countries - something they'd banned since WW2.