i didn't RTFA, but perhaps what that quote is trying to say is that you should choose something that's VERY hard to implement properly but easy for consumers to use. simple interface is key, but if the implementation is also super straightforward, then there will be tons of competitors or opportunities for scooping.

ideally, it would be something that you have special skills in implementing but other founders might not. one example is start-ups spun out of university research projects (e.g., VMWare, biotech start-ups).