I would say that technical insights mean having a futuristic prediction on technology advancement, for example in the 1990's recognizing that the internet would eventually be utilized worldwide (which led jeff bezos to quit his job and create amazon); or in the year 2005 recognizing that the world is becoming increasingly mobile (which led steve jobs to invent the iphone).

For your example, PageRank is actually just the algorithm that Larry and Sergey came up with that ranked webpages better than the existing solution, whereas a technical insight would be that the internet would hold all of the world's information and that being able to find the most relevant information would be crucial.