I've misused the word "possible": I meant to say that if the theory is equally-capable of "explaining" two mutually-incompatible states of affairs, it does not actually have the explanatory power that all scientific theories must have. Which, yes, I think "falsifiable" is the correct word for that. (Although, you'll note that my explanation of "falsifiable" is not precisely correct. I think I've convinced myself that there is no logically-precise definition of "falsifiable", and that it inherently leans on some intuitive notion of "possibly-falsifying evidence" which we have to take for granted, like philosophical induction.)
However, that was itself me being lazy, because Blanchard's typology does make concrete predictions about what sorts of people exist. The assertion that people can be classified into "attracted to women" and "not attracted to women" is refuted by the Kinsey Reports (and many better studies besides); the assertion that being trans is a sex thing is refuted by the existence of certain ace trans people; the assertion that transition is about imitation is refuted by the existence of certain non-binary people…
Of course, Ray Blanchard himself bolts on new categories whenever he can't fudge the analysis to fit a pre-existing conclusion – last I checked, he had around 10 categories – but most adherents treat the original two categories as dogma. (The lengths to which people will go for a gender binary…)
Really, I should say that if you're cis and relying on thought experiments, Blanchard's typology is unfalsifiable: you will simply not be able to observe any evidence that refutes it. I myself (not then having much contact with out trans people (if we discount Reddit)) had to do a lot of introspection (could I rule out self-deception? wishful thinking? how?) before I concluded that either my internal subjective experience refuted the typology (and its variants), or I was too insane to be capable of reasoning. This tendency towards solipsism did not do me many favours (and was ultimately quite harmful, for reasons I will not discuss here), but it did at least prepare me for the many other academics who talk out of their arses about things they have no legitimate claim to expertise in, save for being among the first academics to study it. (Or, in Ray Blanchard's case, among the first academics to study it after the Nazi purge.)
