Or by cisgender do they simply mean female women ?
They do.
The Other Side are all about words creating reality, so to understand reality we must analyse the usage of words. Out in the wild, not chained and dead in a dictionary.
The people who use 'cis' and 'trans' to denote the two subgroups of 'woman' are extremely consistent in their usage. Pick any thread you like on the topic, and see for yourself; it's really quite striking.
When it precedes 'woman', the 'cis' prefix is used for those born female; the 'trans' prefix is only used for those born male.
In a perfect mirror, when the following noun is 'man', 'cis' denotes those born male, and 'trans' those born female.
Whatever the dictionary, the doctors, the activists, the shouty twats on twitter, or anyone else may say, in the shared social reality we create with our words, 'cis' and 'trans' function to indicate sex.
That's how they're used. And we're always being told: definition is determined by usage.