I see cis as something similar to using the phrase neurotypical. It would be hugely offensive to say normal people vs people with autism/Downs syndrome etc. So in that vein I can understand using cis to differentiate between trans women and normal women, and using it makes no difference to me in those discussions
Actually this is quite a useful comparison.
There is autism (and a couple of co-morbid conditions) in my family, friendship group and relationship.
We do tend to distinguish between 'ourselves' and 'the others' when talking to each other because it's a handy way of us talking about ourselves with autism and all the other people who don't have autism.
Probably much in the same way that some transpeople (who refer to themselves as women when they are TW) find it useful to have a signifier to make the distinction for themselves.
However, I don't expect the rest of the populaton to accept that descriptor and call themselves neurotypical too.
But it isn't even analogous because the term neurotypical isn't ever used against people as an insult.
People with autism don't sneer "you're just an NT, your opinion doesn't count" at someone.
People with autism don't threaten NT people based on their NT status.
I don't understand why women are so willing to use it when it's a perjorative term that was coined by a group of males who hate us enough to wish and cause us harm and carries and delivers such malice.
Women don't need a qualifying label;
Women isn't an 'umbrella term'..
Women is fine.