It was NOT a mistake.
Madara said both can't leave that place with their current bodys, that means Obito could not leave in the state he was in, now pay attention to page 15, the Zetsu on the right looks more like a Zetsu-Suit to me (there is a hole on the left arm side and probably also for the legs as well). Obito is using that Zetsu-Suit = Tobi.
That explains these things
His height:
- He was about the same height as Minato, pretty much adult size, Zetsus are adult size.
Loosing his arms: (LEFT is Obitos "human" side, RIGHT is the one that got pretty much replaced with "Hashirama's DNA").
- First arm injury: His LEFT arm dripped off when Minato hit him with a Rasengan, Zetsu Goo AND blood came out of that sleeve = Obitos left side = Human.
- Second arm inury: He ripped his RIGHT arm off after it got infected by Torune, that was just Zetsu Goo = Obitos right side = Hashirama DNA.
- Third arm injury: He lost his RIGHT arm against Konan, it was also just Zetsu Goo = Obitos right side = Hashirama DNA.
Why his Sharingan is activated all the time:
- His right side got replaced with Hashirama DNA thus his Sharingan can't be deactivated hence it's not an Uchiha body on that side where his Sharingan is.
There you go, simple and easy no overthinking needed.
Yeh that's right.
It was probably a Zetsu clone fighting Minato and a Zetsu clone which met Itachi. So it wasn't Tobi !
Look closely at the page, when Itachi met "Madara" in the forest. It couldn't be tobi.
Madara is way taller than Itachi was, but right now Tobi istn even higher than Kakashi is.
Kakashi is just a bit higher than Itachi.