Why bring up cis women specifically? If this response/behavior is in fact real (which I have many doubts on), you could well theorize that it is related to female hormones, which transwomen who have transitioned have as well.
you could theorize that, you could also theorize that its not just hormonal and a combination of other things on the X chromosome, which trans women do not have. so its too limiting to attempt to isolate just hormones.
the babies are the ones emitting the chemicals, we would just need them to bind to us to trigger any number of processes.
we can have chromosomal sexual dimorphism on the olfactory glands, within our lungs, on our skin, somewhere deeper in the pipeline, different gut microbes, you name it.
even if we desired trans women to have these features merged in retroactively, we still need to study the cis women created via selective pressures to understand what exactly the features are
this requires natural born females responding about their experience, so it would be counterproductive for trends to get in the way of choosing the accurate sample population
