I am not a neurologist nor a doctor and I am entirely guessing, so I should not even comment, but some people may not be affected by small amounts of amino acid

I am not a neurologist nor a doctor and I am entirely guessing, so I should not even comment, but some people may not be affected by small amounts of amino acids like this depending on their diet, gaba receptors, existing amino acid intake such as already drinking green tea or using arginine or citruline, or other medications. It is entirely possible that your α waves are already elevated from something else or that this amino acid isn't metabolized correctly.