Personally, I much prefer to learn about sex dimorphism in analytical/academic contexts, rather than in emotional/social ones. I actively seek out and read papers like this in my free time.
Microbes in your gut generally aren't checking sex chromosomes. They interact with sex hormones (see Rizzetto et al., 2018 cited in the paper for this very thing) which often reflect sex chromosomes. Hormone levels or response may not match what is typical of sex chromosomes for a number of reasons including: 46XY women (androgen insensitivity), trans people on HRT, women post-menopause, and sometimes cancer treatment.
IMO it would be less alienating and lead to better health outcomes for everyone if we talked more about testosterone-dominant or estrogen-dominant endocrine systems (or other systems as appropriate).
Also whether dimorphic effects are a result of a one-shot process (e.g. grow testes or ovaries, grow breasts), or a recurring process (hormone levels triggering lactation, sweat patterns).
Basically, transgender brain has some sex-differences that resembles the gender that the person identifies as, and that is before hormone therapies has been applied. If they did such study on antibiotics then you would likely have to do multiple ones, including if the person have taken hormones before or after puberty.
So, research into the impact of biological sex on medication, and similar, doesn't really seem alienating to me. Despite the existence of trans people, there are obviously two main categories that people fall into in a medical sense.
That said, I do think it would be a mistake to assume that the conclusions of any research into biological sex can be directly extrapolated to trans people. If we know that the relevant mechanism is hormones or chromosomes we may be able to predict effects on trans people--but we also might not be able to, if the mechanism isn't known, or for whatever other reason.
One well known example is that trans women's risk of breast cancer is more comparable to cis women than cis men. If I recall correctly, this is because the relevant factors are basically whether a person has breasts or not, and of course, trans women grow breasts when on estrogen.
seems to me that those who insist that gender and sex are distinct also heavily imply that biological sex is mostly meaningless, so its unclear what they actually expect anyone to care about
Gender (either socially ascribed or gender identity, though those two can differ from each other) and biological sex are objectively different things.
Most people who value gender identity rather than the particular indicia of biological sex other people prefer as a basis of socially ascribed gender generally view biological sex as a multidimensional space which includes (among other things, some of which are mutable) gender identity, not a simple binary (even if the distribution may be strongly bimodal.)
> its unclear what they actually expect anyone to care about
Generally, gender identity rather than other factors to the extent that society divides people up by ascribed genders. But also generally a lot less gender segregation, and especially strict binary gender segregation, at all, and when distinctions need to be made to which particular sex- and/or gender-stereotyped traits are relevant, to make distinctions on the particular relevant trait rather than by stereotypical association.
This is a puzzling statement to me. The whole concept of being trans requires that there is a distinction between gender identity and biological sex. If the latter didn't matter at all, being trans wouldn't exist. If anything, trans people would surely be the most aware of biological sex and it's impact on them, as they are not happy with it?
To me, it's like saying an adoptive parent is trying to imply biological parenthood is meaningless. Surely those who wished to have biological children but could not and adopt instead are often the people most sharply aware of it?
In contrast, trans people are usually extremely aware of their biology and related medical requirements - to a greater extent than many others. Like any other topic that might be sensitive, the best approach is to be respectful, accurate, and specific. For example, don't do the thing up-thread of banging on about how "gender isn't relevant to this conversation" without really having that insight.
Largely, this is a problem with society for telling them they are lesser for that, and people having treated them badly because of that, which they have then internalised as shame or a feeling of being less than.
In the adoption example, I would argue that it is not a product of society, but just very present in society. I don't have data to back this up, but kids seem to be innately cruel about things like a peer being adopted, and I don't think it was programmed into them from society.
We are pretty advanced, we can do more than throw our hands up in the air and say "that's how it is" when faced with problems. If we choose not to, it is exactly that: a choice.