That really isn't true, even with a pinyin IME. More so if are talking about spoken Chinese (used for chat) vs. more colloquial written Chinese. Prediction really does speed things up (on my old nokia back in 2002 I used to be able to text faster in Chinese than in English).

Have you seen people type Chinese in a T9 keyboard? My wife grew up in China and typed using that method and faster than her English typing.