From what I think it's supposed to be some type of flashback as to WHY Lewellyn gravitated to our MC in the first place.
We had seen in an earlier flashback that when MC was looking for a job he took one that specified "no questions asked" or minding your own business or something, which was the prison job where MC and Lewellyn first met. Lewellyn had said something about MC losing his memory so it's just a past event MC doesn't remember I guess.
Lewellyn being a dog is more metaphorical, and he's been treated/told he's a dog for god knows how long so he somewhat believes it himself to some extent.
I don't get it is that an alternative time line from the past. Is Lewellyn a dog there? I'm so confused