Some do pass 100% due to the threshold effect,
if you're close enough middle ground on all parameters for all observers.
The problem is that often a TS will think they're actually within this threshold
where there is no doubt, when others disagree. If others disagree, well
you're not passing 100%.
The mythical passsing 100% should leave no doubt NO MATTER WHO LOOKS AT THE PERSON!
This is indeed very very rare. I'd say that 99% of TS don't reach this level including me.
If I go to Japan, well I KNOW my passability will be shot to hell!!!
Because of height differential and the fact that when you skip culture,
what's considered female in physionomy or behavior will be so different.
This is an extreme case, but even in ONE big city, there are many different
public and I know that its with recent immigrants from some country
that I get read much more frequently (Instead of happening 1%, goes up to 5%!).
People of the same background and physionomy are least likely to read you, because
that's where you'll be closer to the group average for women. When people
say they pass 100%, its usually according to this frame of reference
(and this one is INDEED VERY POSSIBLE), since its very hard for me, or anyone,
to have the other point of reference and know for sure what people from
that other point of view think at all time.