I could be way off base but I interpreted Eder's quest as not really being about Elafa and Beorn at all, but more about Eder having a little crisis about the direction of his life. I think he was kinda coasting along on his adventures, thinking that he'd get around to settling down "one day" like he always thought he would, and then was blindsided by the possibility of having a son, and was surprised by the strength of his own feelings about the idea. But then he very quickly discovered that Elafa is dead and Beorn is already grown and it sort of slams the door shut on this possibility that had existed in the back of his mind for a long time, and again the way he feels about it probably surprises him. I don't think Elafa was a one true love kinda deal, I think Eder is in shock and in mourning over the death of a dream. Kind of a midlife crisis I suppose, but the reverse of the one you see more often, which is someone bored with their life who wants excitement.
Anyway that type of feeling came off as very natural to me. I'd have liked to see Eder as a romance option but I didn't mind his quest. If it was the case that his writer just didn't want to write a romance then I think that's a valid reason, even though it's disappointing.