On the other hand, one could view this as TfL tackling a problem which wider society has yet to address, and I think it's a problem which does need addressing. It may not seem overly significant to many, but it's very significant to some. And more to the point, it highlights a very modern dilemma - as a (hopefully) progressive society we now recognise that the simplistic definition of male & female is no longer sufficient to deal with the range of types of people in the world, but we've yet to adequately deal with the practicalities involved in this. The need to be able to collectively address large groups of people in a civil manner, without causing offence, whilst retaining the ability to attract peoples' attention is not the trivial matter one might assume.
It'll be interesting to see how the approach TfL takes works out, it may not ultimately prove to be the optimum approach, but at least they're trying something.