I wonder, is it really a retcon though?
Yes, it obviously is. I agree with you that it was invalid for the writers and characters to say he didn't have emotion. But
they did say it. They said it constantly and incessantly, and they built whole episodes around the premise. And they didn't
start doing so until season 3, after a couple of ambiguous statements in season 2. It absolutely was a change in how the writers interpreted and approached the character. Originally, there was never meant to be any doubt that Data was capable of emotion. The original bible explicitly said that he had "the dominant emotional traits" of the dead colonists whose memories he was built to contain. Even
questioning his capacity for emotion was a change that wasn't introduced until later.
I guess I see it from a different angle than you do. Any changes in Data's personality over the years I attributed to him learning, adapting, and 'growing up' for lack of a better word.
We're talking about two different things.
If I were talking about it from an in-universe perspective, pretending that Data was a real person, I would naturally do the same thing you're doing and interpret his changes as a consistent process of growth. I
have done so, in fact. The things you're saying about whether he really had emotions are much like the things I had Deanna Troi say to him on the page in "Friends with the Sparrows." And I reconciled his more emotional behavior in season 1 with the later interpretation of his character in
The Buried Age.
But that's not the conversation I'm having here in this thread. I'm talking about
Star Trek as a work of fiction, and I'm talking about how the writers who took over TNG in season 3 had a different vision of the character than their predecessors. Just because we can reconcile it after the fact does not mean it wasn't a change in approach.