Originally Posted by Fat Borat
I guess it's just from an order view. I would've expected RBY -> GSC changes, GSC -> ADV changes, etc. Kind of like an evolution of the Pokemon game. Rather than going back in time, so to speak.
I see where Jellicent is coming from with the order - the majority of players are latest gen players, and if they're going to test the waters of old gens, they'll probably start at the latest and work backwards from there. From that perspective, learning what mechanics differ going back in time is the best way to present the info.
As a Gen I and II player only, I also had a hard time following at first, but I'm not the target audience for this letter, so I dig it :)