So why all the hoop-la then regarding the vent hole in the lids? Does
anyone know?

I can understand that it would be a general indicator of quality, but,
in and of itself, it surely can't be seen as a major defect. At worst,
there is a small place between lid and pot where air can pass, in
addition to the air-hole. I cannot imagine that such a "defect" would
ever change the characteristic of the tea, nor can I imagine how a tiny
additional air-hole would alter the pour of the pot. Do please
enlighten!