I don’t really see this as so much an “open ending” as a simple refusal to make the story explicitly yuri. They’re living together, explicitly because they like each other and want to take care of each other; the only thing left open is that elementary school question, “Do they like like each other? Do they like each other that way?”
When it’s done well, I don’t really mind an actual open ending, where we’re not sure where the relationship will ultimately end up, but where the MCs have come to a new understanding of how they feel about each other.
In this case, it seems more like a coy withholding of information, where we could be shown that there’s one double bed with rumpled sheets, but instead we’re shown the toothbrushes and told, “Make of that what you will.”
It’s still been a decent story and I’ve been glad enough to read it, despite its rather evasive ending.