The wandering around just muching grains argument may be fair enough (or not, but whatever), but the first thing that went through my mind was, so THOSE grains didn't count against you for the sabbath like all calories don't count (if you are driving, on your birthday, if you are drunk, or while you are cooking). It strikes me initially with it being a distinction without much of a difference. Gathering grains to eat is what you do during the harvest, too. I imagine some of them are "munched", too.
I continually wonder about the rules that matter to God (assuming you believe there is one and there was ever any truth to scriptures) vs. the things that man came up with over time to "clarify" his rules (like the blood transfusion teaching and the prohibition against smoking)
How much of what made it to the works we now count as scripture were actually "inspired"? Considering the history of its being written, I would submit that there is plenty that was "cleared up" the priests and teachers as they were gathering their followers and encouraging them to 'righteousness'.