as a quality engineer, this weld is acceptable. why waste money doing full weld when u can just tack weld and get the strength needed?
door frame is not structurally integral to the car so it not critical and that weld is probably stronger than the base metal surrounding it.

I'd love to see the welding on other more expensive cars.

based on the diagram, what i'm trying to say the welding of the door does not affect the structural integrity of the car directly.
that is all.  btw the door is supposed to crumple when collided. to absorb the shock.