Important question Brian, It has to do with the chelation bond strength. The chelation agents developed by living organisms like organic acids, amino acids etc, have a relatively weak chelation bond, and readily release the held nutrients. ‘Synthetic’ chelation agents such as EDTA, EDDI, or glyphosate have much stronger chelation bond strength. Frank Dean is a good source of info on this. I would like to have him on the podcast at some point soon.