Are you volunteering to pay for my gender therapy and my HRT medications and my electrolysis? Considering that you feel they are only a "small price" ?
Thought experiment: recall the last time you flew. Now how much did it matter to you whether the person two rows away was "really" male or "really" female as they appeared to be? Would you have prepared different mental emergency plans if you knew that their chromosomes were not what they had first glanced appeared? But you wouldn't have worried about whether the femme-looking XX woman had been taking testosterone and working out and had only put on a femme appearance today because they worried about being refused the flight if their appearance (normally more male-ish) did not match their not-yet-changed legal gender? The dignified short 98 pound young woman, would you have taken more safety measures if he had been forced to put on his man-costume and so look like a miserable "98 pound weakling" ?
What a person wears on the flight is not the real issue for "terror". Whether a proper upper limit on a person's dangerousness has been judged is more important. There is, however, no screening for strength or fighting skills or ability to manipulate mobs or the like.
Have you paid attention to why flights have early landings due to passenger behavior? Drunks, mostly. Belligerent refusal to remove something that is interfering with adjustment of the seats. Making a big fuss because the tea is not warm enough. Panicking because they notice that a fellow passenger is calmly reading Arabic-language news sites (yes, they yanked the reader off of the flight, questioned him, and sent him onward when it became obvious that he was never any threat.) Did I mention the panic over a couple of passengers talking Arabic to each other?
Surely it would be a small price to pay if passengers were prohibited from reading, talking, playing games, listening to music, communicating through sign language, or anything else that could potentially be used to... ummm, coordinate attacks? Discuss targets? Well, we'll work out that part out later, better to be safe, right? Hey you, stop that coughing! And you, don't scratch yourself !!