Maybe it was a promo during the initial launch period. Charging the 2 batteries in the SB with the original charger takes a lifetime. I am surprised it's not standard. Quite frankly I thought it would be. Was surprised when I was told it was an option but very glad I asked. If it took that long to charge and I thought I had the 65 watt I would have thought the charger was a piece of junk.
as far as determining which charger you have there is a significant physical difference. The 27/36 watt charger is about 2x1.5x1. the 65 watt (I'm guessing) is 3x1.5x1. Longer and slightly wider. which makes sense.