Why would it? It's the same materials, same stick line, same brand, same height, same flex rating. Why would one stick be different than than the other? If instead of hockey sticks, what if I was talking about lengths of bamboo? If I cut one length of bamboo to be exactly the same length as another, all things being equal other than starting length, would you be asking that question?
True isn't changing the meaning of flex. The meaning has always been this. In trying to "help" people figure out what flex they should use, someone back in the day (my bet is someone in the marketing department) tried to dumb things down in a way that made flex rating and stiffness became interchangeable when they're not. Generally, this wouldn't be a problem if every stick came stock at the same height, but they don't. Hence why the example I gave can be confusing to some. Remember, according to that video, the flex rating is calculated at a distance of 1m. Stiffness takes into account the whole length of the object. Unfortunately, each stick doesn't come with a stiffness rating.