No, it's always been a lie to make himself feel like a decent man when we all know it's his ego. The flashbacks of gray matter prove that's who he's really been all along, but the final one of them buying the house, it shows his ego has always been there. The show is trying to say it was never for the family, it was for Walt's own ego. Thus ruining the fact thinking hes a badass & is just pure evil. Just how Vince sees him
I think there are two elements to this. At this point in the story, we ultimately have two characters with Walt:
- Walt (Family)
- Heisenberg (Ego)
You can see Walt snap in that interview with Gray Matter where Elliott and Gretchen are saying that Walt's contributions to the success of the company were nothing aside from the name.
Then when Gretchen is asked if Walt is still out there, she says "No, at least not the sweet man we once knew."
In Walt's mind she is essentially saying "He is no longer the doormat we once knew."
I think it's been obvious from Season 1 that an element of Walt's motivation is a lack in satisfaction of his life and a desire to provide so much more, and a belief that he is capable of much more.
There are several underlying motivations towards why he did what he did, this scene in particular snapped him out of Walt-mode into Heisenberg-mode.
The phone call with Walt Jr. was Walt-mode, and his motivations/intent were to provide for his family in what little way possible given his current circumstance (fugitive in hiding, unable to reach out to civilization while he has a death sentence with cancer). Walt was ready to give up until the Gray Matter interview brought out Heisenberg.