Both my cars were tagged as exports, and both have the defrost option.
Over here, I've seen many coupes with the option, practically none on fastbacks.
So I don't know if it's really a rare as option, but what is truly rare, is having the knob on the defrost that is not broken.
I've never seen one not broken in real and both my cars are no exceptions.
Planning to buy convertible switches to be able to finally have the knobs.
As a side note, I was lucky enough to score years ago a spare rear window with the grid for the coupe.
When I was driving the 73 daily, I must say it was handy and used it almost every morning during winter. I use also the grid as antenna and get much better radio reception.