I doubt how many of the peer ratings are based on who was most effective against them. I'd imagine it's a distinct minority. A lot is style- either a skillset that impressed them, or that they found difficult to play against.But that's because of a difference in styles presumably. Players can find awkward bounce more difficult to face depending on their own batting techniques. Doubt anyone is actually saying Morkel is a better bowler.
Difference in style explains a lot of player ratings. Bowlers with the widest range of skillsets and aggressive bats are generally rated extremely high.