The reason why I decided to put ~another stories~ under independent title is precisely because it consist of only 3 short stories tied to "Bokura no Kiseki" story and the others are independent 'one-shots" ;-)
What connects them? The same author. You can see how Kumeta-sensei likes to develop her story compressed in one chapter. They were in Arcana, yes, but only 2 of them were somewhat translated already, the rest was not.