More due to the alkaloid levels and the fact that part of the dose is oral. Think about it, a mucus membrane is a mucus membrane. Of course it would be a less efficient mucus membrane and part would get swallowed, but the statement was.
Ya ever hear of, "A pinch between your teeth and gums."?
So often people want things to be binary. Not working as well does not mean not working at all.
Also, I've never seen anyone rub a couple lines worth on their gums.
Epilogue:
An Experience with Coca. 'Chewing the Leaves' by chewchew
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