Why would you need T9 on a touch screen? You can just display a full keyboard. That was the defining aspect of the keynote that launched the first iPhone, even.
Because the T9 keyboard is already displayed, and the full keyboard isn't. It is a very fast way to search through your contacts directly from the dialier when I want to call someone, which is the primary use case of the dialer (calling someone already in my contacts).
There's nothing "astonishing" about it.