The term "wall of text" comes from forum discussions, it's pointless to use as criticism for games (let alone books). People do use it as a derogatory term when the text is not interesting or is way too long for it's trying to accomplish. In that sense, PS:T has very few indeed.
Also, PS:T is not nearly as wordy as people make it sound. The actual word count is around 700-800k words, significantly less than TTON, BG2, NWN and even D:OS2. PS:T seems wordier than it actually is because it doesn't have as much combat as other RPGs, its encounters don't last as long, and the writing is much more memorable than the action parts.