A very rare William Trevor story that feels incomplete

The strangest thing about William Trevor's story A Perfect Relationship, in his "Selected Stories," may be the title. Is it perfect? Can any relationship be so? It's on the surface a story about a couple, been together about 3 years, man quite a bit older, met the woman when he was her teacher in a night school, teaching languages, relationship built slowly, now she lives with him but decides to leave. Like many relationships with a large gap in age, this one carries overtones of master-student - he's gradually making her aware of culture, introducing her to serious cinema and to classical music, one composer at a time. There's the sense in these relationships that the woman will grow out of her dependent, subservient status and leave - maybe for someone closer in age. There also Oedipal overtones in these relationships with a wide gap in age. The story surprises us, however, as so many of Trevor's stories do: we alternate between his and her POV, and from hers we see that she's not really clear why she has left and she has no goal in mind, just a desire for a little more independence. Most of the action in this somewhat quiet story is from his POV, as he goes to see her parents in hopes that she's gone there (she's an only child, very insecure and not confident in her looks); the mom has always thought the relationship was bad for the daughter, mostly because of the age difference, whereas the dad is much more supportive. In any case, she's not there - guy goes back to London, very morose, and then, bang, she turns up, ostensibly to drop off a key, and stays. What's it all about? These May-December things can work out, sometimes? I think there's a darker undercurrent - she's pushing for something she doesn't have and he can't give her, this story isn't really over yet. One of the very few Trevor stories that I think could use more development - it's crying out for the next chapter, and the next, a novel in waiting.