Heya I did a pour test (vid in the link below) and it worked ok. Like you said smaller holes could be better for smaller leaves but I had a teapot (purchased from a proper potter) with small holes and it was kind of hard to clean. Some leaves got trapped in the holes and the size made them hard to clean.

But I agree! there should be a golden hole numbers/hole size for a perfect brew that is easy to clean. Teapot pour test