I wouldn't call "No Productivity" inferior... Its a pretty killer tune in its own right.
I think with these comps, you've gotta take into account also the Six Degrees of Separation links that need to be made in people's minds, as well.. "Nic Fit" with Sonic Youth, Scream and Flipper with Nirvana, the token NYHC song... and like Malto was saying, it probably all fits within the context of the film. I can also bet there were a lot of songs left off the CD that are in the film, as well. It happens all the time. For some reason, the Big Lebowski soundtrack CD completely omits Creedence Clearwater Revival and The Monks.
P.S. -- Malto: What's the deal with this Subhumans re-union shit? They're playing here (at a former strip club, no less) in about a month.