Also, I have my doubts that it is chlorophyll in the plant material that causes harshness.
Degradation of chlorophyll is an active enzymatic process that plants go through while they are at either the end stages of life, as our cannabis plants do, or at the end of growing seasons like deciduous plants and trees heading into winter.
Degradation of chlorophyll in harvested plant material, particularly material that has dehydrated to the point where it is no longer “living” tissue, is most likely going to be broken down by either an oxidation process as the material degrades, or by bacterial agents degrading the material.
Considering that the mechanism of chlorophyll breakdown was discovered less than 20 years ago, there is still a lot we don’t know about the process.