In my experience, there is absolutely no such thing as too much, wasted, or unnecessary knowledge. Everything connects, through metaphorical explanations of one topic using instances from another (think squares and rectangles; a square fulfills all the criteria to be a rectangle, but the opposite is not true), to more holistic and imaginative links, everything is connected.
I cannot for the life of me remember where I read it, but I recently found out that ‘speculative job applications’ are a common and accepted practice in France. A mere few days later, a half french girl came to the desk of the LZ and asked me for what you might call it if you send a company your CV without them officially posting a position. I then not only knew the word – speculative – but also the cultural context to be able to tell her that is a far less common practice in the UK.
As an aside, there is also knowledge in the form of sheer number of encounters with the particular issue at hand, perhaps succinctly known as experience, or expertise. I fitted a pair of new wheels to my bike the other day, with the help of a friend and only one small injury. The next day when I was in a bike shop for an unrelated purpose, and just about to leave, the guy said “just before you go” and came and switched the quick release lever to the other side, as, he said, on the side I had it it could get in the way of the rear derailleur. It was an excellent point, but of course if you see dozens of bikes go through your shop every day, it becomes easier to spot irregularities and correct them, because you have more experience of the variety of ‘correct’ ways different bikes can be assembled