Farmer Job-Nether Wart

Nether wart is a farmable crop and I thought that since it was a crop it should count towards the farmer job. I was surprised when I made a farm for it and planted the nether wart and it didn't give any xp towards the farmer job, or when you harvest the crop.
My bad it does count towards harvest but not when planting. But other crops count when you plant them so why not nether wart?