I'd say no.
To use the same example: matte paintings are done for many productions that aren't SF/F—historical dramas, for instance. If you look at the matte painting article Keen linked, only about half of their examples count as SF/F.
The same goes for pretty much every other SFX technique (note: SFX stands for "Special Effects," not "Science Fiction").
I expect SFX questions will be completely on topic at Video and Film Production when it launches. That proposal is currently in its commitment phase, so if this aspect interests you, go help out!