Why is Oscar the TV counterpart for Dexter and Tomas for Thomas Richards?

It makes no sense other then the fact that Robert Kirkman said so. But they're nothing a lile. Tomas is basically Dexter, he wants the group to leave and then tries to kill Rick, resulting in Rick to kill him. But then people say that Tomas is Thomas Richards, other than there names being the same, they're is nothing. Thomas had glasses, killed two little girls and attacked Andrea, but Tomas never done any of that. Then their is Oscar who is the "TV counterpart" to Dexter. They are not the same people, Oscar is nice and Dexter is a villian.