The other half is bound up with that 25-cent word, hermeneutics, which is a complicated name from philosophy for the study of what we know and how we know it.

This is not quite what hermeneutics means, epistemology is the study of knowledge (what we know and how we know it), hermeneutics is about interpretation and how we derive knowledge from the interpretation of a text, or in this context, interpretation of experiences.

The title of this article is a bit click-baity, transness is not like left-handedness in a million different ways, and nothing about the typical comparisons between transness and left-handedness are actually wrong or critiqued.

tl;dr trans people are able to interpret their experiences now where before we lacked the tools, so more of us are able to correctly identify ourselves as trans; the same thing happened with sexual assault of women btw:

https://en.wikipedia.org/wiki/Epistemic_injustice#Hermeneutical_injustice

The concept of hermeneutical injustice comes from the feminist philosopher Miranda Fricker.

The main related paper linked to in the OP is: https://philpapers.org/rec/GEOHB

I think there are metaphors that are helpful to trans people and there are metaphors that are helpful to explaining transness to cis people. The left-handed metaphor is definitely in the “for cis people” category imo.