Buy supplements in POWDER FORM when possible if you don't need enteric capsule, etc.
It eliminates other contaminant/padding, no capsule materials to worry about.
You can then also vary the dose size to see if there is a tipping point where it works.
For all we know the author was overweight and the mg of Theanine vs KG of weight was not enough for any effect.
And Theanine DEFINITELY "works for me". Not even a question of doubt.
I always take a 1/4 teaspoon before bed. If I forget on rare occasion I find myself wondering why I can't fall asleep until I remember.