no you are not right at all..

miners having 51% of the power to produce coins for very limited period of time is not the same thing as stake holders with 51% of the coins and the power to create 51% of all future coins for eternity.
this is why the vericoin devs had to take such drastic action when someone had a mere 30% of the coins.

also a pool having 51% of the hashing power is not the same thing as a single entity having that much power because miners would simply move if the power was being abused.

pos and pow have very different problems.