I don't know what he means but I wouldn't wear slicks in my technical. I suppose it varrys. Slicks would be useful in bmx style technical with lots of concrete and some manmade obstacles. Otherwise slick are only useful for picking up some speed on a mtb.
Technical out here is the northshore style riding (extremely advanced) or very rocky (rock gardens or even boulder hopping) and very rooty and wet (typical for bc). You would get hurt if you rode slicks out here
