The tech names are purely there for flavor and represent stages of advancement in Western technology by a certain year (which is why you get penalties/boni for being ahead/behind in time). I highly doubt that the only thing that was discovered in around 1700 was that limes prevented scurvy. I just so happened that Paradox thought it fitting to highlight that one particular advancement (which did not even apply to most European countries, so it makes little sense to say that the text is relevant to everyone who researches it).
Yes, it seems a little quirky that limes coincide with the when the concept of client states developed (and that statement isn't even accurate), but like people say, it's an abstraction for gameplay reasons.
