Why 't' and 'f' instead of TRUE and FALSE
PostgreSQL does not return these instead of boolean values.  It is some clients (for example, psql and pgAdminIII) which represents TRUE with t and FALSE with f - try the same query in another client and you will see something else.  See, for example, what DBVisualizer gives you:



I guess the reason for showing t and f is simply sparing space in a command-line client that lacks horizontal scrolling abilities.

Note: I am in no way affiliated to DbVis Software.