This is a good question to pose, Blaine as I've noticed that in the past as well.
Not to hijack, but I have noticed in one of my ponds where I have high qtys of GSH and FHM stocked the FA is nearly nonexistent. I can't explain it as other ponds with the same chemistry have significantly more FA - all other parameters being equal to my knowledge. Could GSH and FHM also be targeting FA?