I get that they must think the main audience for the Blu Ray release of the anime will be established fans who already read the novels, but I find it a weird move to put a story set in the future as an extra, imagine someone who only watched the anime suddenly skipping that far ahead.
But as someone who has read the novels, it's just delightful, I was hoping we'd get more chapters set in the future and this was a very nice one. It does feel like it should just have been a regular chapter like that other future one from volume 8 since it covers an important part of Adachi and Shimamura's relationship, in fact you could pretty much add it to volume 9 and it wouldn't feel out of place.
The one thing that somewhat bothers me is that it feels like the author is holding back from showing them being more intimate, though I understand he probably doesn't want to "spoil" things like their first kiss or more by just having them be a regular occurrence in the future chapters and thus make them feel less special when they will eventually happen in the present timeline.