Well, that was a Sam focused flashback, just as Something Wicked was a Dean focused flashback. But both of them showed both kids as victims of John's neglect: the fact that Dean had to play John's part for Sam wasn't told from Dean's perspective, because it was Sam POV, but it was there in the narrative for the audience.

It was Sam POV partly because of the role reversal that was happening in current timeline, and partly because it was also about Sam finding out that John had lied to him all his life, which was Sam's particular part of the family dysfunction drama, just as the overresponsibility of Something Wicked was Dean's, and from Dean's POV.

I don't think either episode by being focused on one child glossed over the fact that the other was also involved in the neglect.