Here's my thinking; garlic is food and excess food has to be processed which means the
nitrogen cycle. I feel certain that I use more than 2 drops per teaspoon because I use 2 or 3 drops and never feed as much as a teaspoon of food. In fact, it is probably more on the order of 1/8 teaspoon which means that I am grossly overdosing garlic. I see no ill effects and the nutrients in my tank are at zero.
Most of the references to garlic are anecdotal and I doubt that you will find any definitive information on this. That being said, I think that there is benefit to using garlic and I plan to continue to feed it.
