I have found that in general women do sleep colder than men. Not always, but more often than not. I sleep LOTS colder than my husband. I do not know if we sleep colder or or more sensitive to our environment and LIKE to be warmner. I also think if women actually had bags that fit them properly, they may not sleep as cold. I do think women get colder in different places. We usually have hips that are bigger, and most of our weight rests on hips, therefore, hip area needs more insulation. Most mens bags have more insulation in the shoulder area.

I do not think people are good at rating sleeping bag warmth. Every person is different; every night is different. Hard to get consistency. I suspect lots of manufacturers simply measure loft and then rate based on loft. Not a great method, since actual design and personal fit mean a lot.