I am noticing the same thing. I received my phone on Apr-30.
Even i also pre-ordered from nokia website and the phone becomes too hot while charging.
Also i got 8.1 with april security patch pre-installed after unboking.
Dod you guys also got it pre-installed. The devices sold via amazon received the update after unboking.
I am also facing same issue, pre-order it and got it on 30th Apr. Can moderator or somebody help in this?