I've also had the same thoughts about "New World Order" stories where only women are affected by changes and where the trans and non-binary communities fit into the narrative. Of course its going to depend on the person, but most go with the "Virus only affects XX Chromosomes" line of reasoning, which is certainly a more neutral approach, though rarely in those stories are trans people involved to the point where the readers would see how they are/aren't affected physically and socially.
There's also a side of the community that embrace the gender bending side of muscle growth anyways, but those stories (including my own) tend to still be focused on CIS males and females. I've been wanting to include more trans and non-binary perspectives in my stories, but its difficult for me as a CIS male to properly convey that point of view, I'll admit. Plus there is a difference between including those perspectives in stories as a means of broadening the breadth of characters and personalities, and purely servicing a kink. It's a fine line to walk to be sure, even among stories that are supposed to be fetishy!