Yes, Apple definitely wants the iPad to work as a computer replacement, but they also recognize it's not good enough as a replacement for most power users (yet). In fact, in the same article as the "why would you" quote, Tim Cook goes on to say the iPad Pro can replace "a notebook or a desktop for many, many people". "A notebook or a desktop", unlike "a PC", does include Macs, but saying the iPad Pro can replace them for "many, many people" implies it can't for others.