Am I correct in my understanding that a single-stage rear defroster was standard in '72, but the dual-stage was optional?

I'm looking at all the various things I'll want to deal with while the glass is out for paint, and the rear glass and defroster is an open question.

The car is wired for 2-stage (brown, red/white and red/black). It has a two position switch. The glass now in the car (with a probably non-functional grid) looks like single-stage (9 grid lines, no obvious zones, and looks like there would have been only 2 connector tabs if they weren't already missing).

Wouldn't surprise me much to find the rear glass is not original. But while I don't have a CoA or whatever they call it now, I do have a verbal report of the car's option numbers that was obtained from Porsche by someone in the UK. That list of options does not list 2-stage defrost. Nor does the Tourist delivery order form for '72 list it.

I've seen that the 2-stage may have only been available with full tinted glass, which my car does have (option 568). Did full tinted windows include the 2-stage defrost in '72? Inquiring minds want to know...