Tranny (and more-so shemale, which is also used in the press release) has been used as an othering/marginalizing word and as hate speech. The community has rejected this term, and prefers trans/trans*/transgender. GLAAD has made this very clear in their literature:
http://www.glaad.org/transgender and I'm surprised that a website featuring trans women and made for people who are attracted to them would circumvent any thought on the issue and go with what's easiest, regardless of how this perpetuates a word that has fallen into ill-repute.