I get the idea of a the good aspects of over-flowing cups.
You have plenty; you’re set; you’re good to go; you have more than you need. I guess that’s all well and good, but a spill all over your table is not a good thing. I think I’d well prefer a cup that was full, but not overflowing.
(Note: Sake bars in Tokyo go for the best of both worlds by serving sake with a cup in a bowl. Then they proceed to fill the cup until it overflows into the bowl.)
Quirk it: 0