To me a parking lot coaster is one that is designed so that it can be relocated/cloned easily and often. Not every ride location is conducive to a lot of interesting terrain elements. A key feature of the parking lot coaster is supports that all go to the same "0" and are at obvious regular intervals (for easy placement and reuse). Go to a Six Flags, you'll notice that every footer is the same height regardless of the terrain. The same goes for Glissade and Die Wildkatze. Also, a condensed foot print that sort of can work anywhere is another qualification.
Being short does not make you a parking lot coaster. Being a cheaper coaster is not parking lot. I think sometimes Griffon and DF get a sort of bad rep because they aren't up to the par set by LN, BBW, Alpie, and AC. In any other park they are just fine (well maybe not DF, but I'd ride DF 1000 times in a row before a single ride on say Shockwave or any other TOGO), unfortunately at BGW they are *relatively* bad.