Eastern Orthodox theosis teaches that humans become “partakers of the divine nature” (2 Peter 1:4), and Athanasius said God became man that man might become god. Isn’t exaltation being presented as uniquely Mormon when it has Christian parallels?

The parallel is real and Latter-day Saint apologists use it. The difference the Orthodox insist on is that theosis is participation in God’s life by grace, never becoming God by nature or becoming a god of the same kind as the Father; the Creator-creature distinction is preserved absolutely. LDS exaltation, as taught by Joseph Smith in the King Follett discourse and by Lorenzo Snow (as God is, man may become), is becoming what the Father is, on the premise that the Father was once as we are. That premise is what theosis never held, and it is the point of difference.