Given the context of the translation, I think you are reading far too into it my friend. The subject is about Madara, and Tsunade is trying to give a valid reason as to why she wants to use the other technique to get to where Edo Madara is at instead of using the FTG technique.
She decided to save the FTG technique for summoning the Mizukage as a strategic move to make the most out of their transportation Jutsu options. If she had chosen to use the FTG tech on herself to port out to the battlefield, she would have ended up where the Mizukage was already, but not where Edo Madara was at.
So basically they decided to maximize their power on the front against Edo Madara by getting all the kage together, which required her to use the other transportation technique instead of FTG.
If you notice, it takes 3 of her guards to do the technique, and they aren't just any low level ninja. I don't think that the technique Jiraya was talking about was the FTG, and I don't think Naruto will be in line to learn it.
IF they use it in battle, it will be to bring the real naruto to where the Kage are at, except they could have done that already, and didn't. The only other option will be to use it against Edo Madara but have her guards combo it with Naruto. He doesn't have the time nor the level of understanding to learn it himself, much less use it.
The technique Jiraya referenced that would require Naruto to have the key to the seal is the one where he goes chakra mode with the demon fox. Without the key, he never would have been able to learn that jutsu.
At this point, there aren't many options left for Kishi except to have the Kage fight Edo Madara. Naruto wouldn't be able to fight him because he can control the Kyuubi and release it from Naruto's body.
That's why his Kage Bunshin used up all the fox's chakra that was inside of him. To keep Edo Madara from releasing a miniature Kyuubi.
As far as A's arm goes, I think that was just an error on Kishi's part. Unless Tsunade's Genesis Rebirth technique healed his arm back the moment they touched down, he shouldn't have his left arm. On page 14, in the panel where they port into combat with Edo Madara, you can see where A's clothing suggests his left arm is no longer there. Plus he's using his right arm to punch the other ninja.
My money is on 'honest mistake' or 'Genesis Rebirth' explaining A's left arm.