ooh, i like this! so first of all, this is just my hc ofc. but, i think it's complicated? yes, and no.
I think he's primed to be afraid/apprehensive of losing people because of Niwa and the boy, we know that he sees losing the people he loves (even if he won't admit he loves them in his way) as a betrayal.
still, Scara is a reasonable individual (for the most part lmao), he knows that Niwa and the child were both more physically fragile than Nahida, her being an archon.
again, this is just my stream of consciousness/thoughts, and honestly I hadn't thought much about this before this question so thank you anon 😊 so i think yes, in a way he is- i don't think he's completely healed from losing people in the past. i hope he'll get there one day! but there's still that fear, I think. Even if it's irrational, or even if it's to something like her opinion of him changing rather than sickness or dying in battle. And I do think she's very important to him, she showed him kindness and understanding when no one else really did. saw him as a person when everyone else he knew treated him like a thing to be used.
now i'm thinking about their comparative lifespans...hmm...(sorry it's v early and im running on 3h of sleep here)
let me know your thoughts too though im curious!!! 💕