why would the game developers make up stuff? that's like giving sasuke water element in the game, because as you say, games do not count as material. Am I right?
Geez, are you really asking that?
1.I don´t know if Tsunade has or doesn´t have lightning element, i don´t recall it being stated in the manga.
2.ONLY things that happen in manga are official canon, things like games ARE NOT.
3.Game developers and publishers would do that because THEY CAN!! and they pay up good money to get licenses. For the most part they try and stay faithful to the original events, HOWEVER many many times they decide to go and add their own spin to things just for fun or just because they want to add their original touch.
Proof of this is the whole DB Tenkaichi or DB budokai game sagas, where game developers have made up fusions THAT NEVER happened in DB universe, thus altering the original and canon events in DB.
Now, you may ask yourself what does a DB game have to do with a Naruto game? Namco Bandai is the answer they are the ones who own these licenses to create both Naruto and DB games, if they did it in a DB games WHAT would stop them from doing it in a Naruto game?
Bottom line, everyone knows games ARE NOT canon at all...Manga is.