Of course it was ingrained. And really, anyone who paid enough attention could tell that Hitsugaya wasn't always the most subtle in showing that he cared for her. A look at the network could confirm that, with the way that he openly interrupts her conversations if she's speaking to someone he deemed dangerous, or who was trying to drag her into trouble, or simply being inappropriate with her. It was a reflex, an instinct.

Around Hinamori, this was usual.

He just shrugged at Hinamori's reaction. "You're always stealing my food anyway, stupid. I might as well save you the trouble."