Bill what the groove does is it picks up water and helps to keep the cavity hole clear. works but you need the hole bigger. when i drill the hole, I give it a tilt forward also.
I learn something new every day. Sometimes many things! I too, usually drill those tiny holes out a little bigger but I have always worried about allowing too much water to blow into what is supposed to be a drain. I guess I will stop worrying! I am also going to keep my eye out for that scoop feature. I swear I had never noticed that before!
Long live American manufacturing!