Between Son-Chu's nonfunctioning automatic shoulder belt and sensory issues possibly preventing him from wearing the lap belt part, I would say no. The Mitsubishi probably has the same kind of seatbelts considering that it's roughly the same year as Son-Chu and used the same seatbelt design, so probably the same thing there. In cars like the Cadillac, BMW and Aerostar, with normal seatbelts, he probably never wore them out of sensory issues.
Would Borb have made him wear it anyway before he got Son-Chu and his license?