One thing I noted the winter after I bought my volvo is that, not only was there a rear window defroster, but side too.

The wrong side.

The rear side window in the back of the wagon, ON THE DRIVER's SIDE
had the wiring for defrosting.

What good would that do me? I can't look out that window with either a turn of the head or a mirror.

I think, generally it is intended to be the opposite side of the driver side.

Was this a production problem? A design intended for right side driver side steering? They never bothered to adjust for cars destined for left side driver side steering?

2002 V70 wagon

I think what you are looking at is the radio antenna, not a defroster.

I hate it when I'm wrong. Blush. I just found an online wiring diagram, and indeed, there is a label for antenna, and it mentions left rear window on it.