Cis is a chemical term means on the same side of.
The idea being that if your gender matches your sex you are on the same side of it.
But gender is just society's expectations of behaviour depending on sex. So stereotypes.
So if, as a woman, you don't conform to them, you're not cis.
And since society's expectations of women are to be compliant, subordinate, underpaid, available for sex, sexually harassed, then no thanks.
Society's expectation of men is to be powerful, a leader, rational, logical. So if, as a woman, you are any of those, you're not cis.
It's also a not so subtle move by TRAs to appropriate the word woman for men identifying as women, and give the words cis woman to actual women.
There is no way on earth I will ever be defined as 'not a man who identifies as a woman'.