I don't think it's too clingy or unreasonable? But it does depend on the specific circumstances and the people involved.

I think Steve would definitely make sure he was with her at least that far. Like, I feel like he'd want to go further, because he's seen some bad stuff and he knows what it looks like when people get hurt, but he'd pull back and reassure himself that she'll be okay. It's not Steve if he isn't worried.

I don't see Darcy being with many other guys who were that considerate though, so that's another element to it.