True, but that’s not the ‘gotcha’ you think it is.
TERFs have never pretended not to use double standards; in fact, they’re very open about doing so, and how they consider that sort of double standard to be entirely valid. A core element of their ideology — indeed, the very basis of it — is that men and women are fundamentally and irrevocably different. And since men are considered to generally be a risk to women (but not the other way round), it follows that women need special considerations and protections from men.
Indeed, you could see them talk about this stuff many times in quotes submitted here to FSTDT, including about how they see trans men.
Basically, trans men are “actually women,” thus weak (and possibly docile), and cis men can easily protect themselves from them. Hell, if anything, it’s the other way around: TERFs consider cis men to be threats to the trans man in question.
On the other hand, a trans woman, being forever “male” — and thus strong, aggressive, and socialized as a misogynist — is an inherent threat to cis women; worse yet, since trans women are thought to be fetishistic perverts and natural abusers, them being a ‘dire threat’ is all but guaranteed.
So, TERFs don’t shy away from double standards regarding gender at all, not even in theory. Quite the contrary: they would consider a lack of such double standards to be dangerously naive.