Currently the "farm 100 nether wart" and "farm 200 carrots" quests increase their counter by 1 whenever you break one of the respective crops. This means you can constantly plant the crop and break it to increment the quest, regardless of if the crop has actually matured. The proposed improvement is that whenever a crop is broken, the quest is incremented by Code: (number of crops dropped - 1) One crop is subtracted because if you plant one carrot and get three carrots, you just farmed two carrots, not three.
I get where you are coming from with both suggestions, but I believe it should be an option for people to do it an easier way. you do not have to do the quests the easier way so IMO its fine the way it is, just like the epearl quest. You can do it the easy way or you can do it the challenging way.