I am installing a Kohler 9132-CP shower drain in a Kohler shower basin, and noticed that there is no inner compression nut used to squeeze the rubber gasket around the PVC pipe, like other manufacturer's use. Kohler's gasket just gets pushed down, between the drain housing and the PVC drain pipe, but has no compression force applied. How does Kohler get away with not using a compression nut on this gasket, like most other's are using? Is this a bad design? Thanks!