but not in a relationship - that will be left an open question.
I pretty much agree with you other than this bit. I don't think it being left up in the air is going to happen at this point since it's clear that Miss Sunflower has some sort of feelings for Matsuri too, even if they may not be romantic ones. Though I am curious how that situation might be handled if she doesn't end up returning those same feelings since the series mostly avoids drama and that sort of outcome would typically be very drama filled.
I agree miss sunflower certainly has feelings- she definitely loves Matsuri imo - but it isn't romantic love yet- or she hasn't realised that it is. What I mean by an open question is if it ends with Matsuri still in love with her - working at the store so they are still together all the time - miss sunflower loves her - but its not totally clear in what way - like right now.
That would leave it plenty open for your own interpretation of what their future would hold- just because the story ended on it never being specifically said what miss sunflowers feelings are doesn't mean they can't develop into more after the story ends.
To not leave that open you would need Matsuri to not just declare her love like she does all the time but ask for it to be returned and miss sunflower to say that she can't. And I don't think this story will do that.