Nothing weird about it, t'was the way things worked back then. There should be a R/S door lock cylinder.

Custom Cabs came with R/L door lock cylinders, Standard Cabs only came with a right door lock cylinder as standard equipment, left side was optional.

For decades, people locked the left door (all automakers cars & trucks) from the inside, then slide over the seat, got out, locked the right door using the provided lock cylinder.

Why? Because many streets did not have painted dividing lines, traffic was chaotic with people weaving in/out. So...automakers didn't want people standing out in the street locking/unlocking left doors.