I think hes saying that in there it said "Tobi insisted that Izuna had willingly given up his eyes for the good of his brother and the whole clan" Which is inferring to the fact that Izuna can't be Tobi. But i dont know what that has to do with anything?
It is possible for Izuna to be Tobi,!! Orochimaru was gonna inhabit Sasuke's body, it could be same jutsu or similar that he's using to inhaibit Obito's body