It appears that Guns, Gunner, Vehicle skills, and Natural Sciences aren /TL skills. Why drop the /TL from the others?
GURPS? A. In full GURPS, all those skills have /TL. But in GURPS Lite, the vehicle skills include Bicycling (which has no TL) and the missile skills include Bow (which has no TL). So we omitted the TL as being not entirely true. And anyhow, the TL penalties for physical skills are GREATLY relaxed in Fourth Edition, so the omission really produces only minor effects. I hasten to add that GURPS Lite for Third Edition did the same. Q. Under Running and Swimming, Move is halved when you are at 1/3 FP or less.