The other toad would be able to sense his nature chakraIf Obito can be crushed by a boulder and be rescued by a legendary ninja called Madara Uchiha who has been hooked up for years into the Mazou in a secret cave.... then why not? I think maybe he transformed into a toad and can therefore not communicate. He thinks maybe Naruto would perform better knowing he will avenge his presumed (I believe) death.