A few tech speed up other techs, or so it states in their descriptions.
I too am interested in why the description says this, but I think it is more likely a oversight that hasn't been fixed yet.
Some history: Civ4 had techs like Pottery, for example, that had required prerequisites, and also "OR prerequisites". In Pottery's case, The Wheel was required, but Either Fishing or Agriculture were required, before Pottery could be researched. All three could be researched first, but only two Had to be... as long as one of them was The Wheel. There were a lot of these sorts of things.
When one extra "OR prerequisite" had been researched, like in our example if all three had already been researched, then all research into Pottery would be sped by an additional 20%. 20% is nothing to sneeze at, and is one of the multiple penalties of the 'beeline' or researching costlier technologies before finishing the ones that are cheaper first. (Another one is that, if your neighbors know the tech you are researching, you get a bonus researching it).
Problem is, this mechanic wasn't documented anywhere. So, the makers of the BUG mod (and others, I just don't know who right now) felt to make that information more obvious, by pointing out which techs were sped by which, in the mouseover descriptions of both. They weren't specific by how much the research was sped, they only included the message you see.
BUG, together with this message, was pulled into C2C, and there remain a few optional techs, but they aren't the same. As near as I can tell, the current iteration of the tech tree contains absolutely no "OR" prerequisites. This, by itself, changes the strategy for research, and I am not sure I like it, but that is probably a discussion for another time.
What interests me is, when BUG tells us that a tech is sped up by another tech, is this just a misreading the XML tags for tech requirements, or is the game actually speeding research for techs with multiple requirements (Tribalism is a great example here). It doesn't look like it to me, but I would like to be clear on that.