FTGlvl2 and Hiraishingiri
We all know this chapter included some early, better version of FTG, done by Tobirama.
Tobirama's Hiraishin doesn't use seals, as Minato does.
Hiraishin is used just for teleportation of the user without any combination.
I think that Hiraishin lvl 2 was a mistranslation, OR refers to the use of this jutsu with another combined. On the other hand, Hiraishingiri implies the use of a sword/jutsu in the process.
This is why Minato said that "His space-time ninjutsu is better than even the Second's". This means Minato<Tobirama in terms of space/time ninjutsu, because even Minato said that, and this is true, because he uses seals, while Tobirama doesn't.
For Minato fanboys/fangirls, I am a HUGE Minato fangirl, too. But being a fangirl/fanboy doesn't mean you can't see the truth.