Is Andranik Migranyan right?
No - because I don't think Putin wants Eastern Ukraine. If he annexes Eastern Ukraine, then the remainder of Ukraine will vote to orientate themselves towards EU and NATO. Putin will then eventually have a NATO country on his border.
If he leaves Eastern Ukraine alone, and works with the West to ensure that what is left of Ukraine becomes a functioning democracy, then it is unlikely to ever vote for EU or NATO membership, and Russia will be able to maintain some sort of influence over its neighbour.
Crimea was different (in his eyes) because it had a very substantial Russian majority and has always historically been part of Russia.