Even in flash fiction it is hard not to world build. I always liked burying things to pick up later, and it kind of plays to what may be a weakness of being an individual working on something – that you can only invent so much; that you tend to have echoes throughout your work that might construe a thematic tendency.
It is hard to understand how a writer might walk away entirely from a creation and not want to revisit. It is almost like the gravity of a story pulls in the other things in the universe you have created and all those astral bodies pass close by the planets you have built.
I write in what I think of as a very dense style, and have almost fallen into a pattern of simultaneously unpacking one story while seeding the promise of others. Do stories really have ends? In some sense no, if they are built with the kind of care and attention to detail that makes them real. I want to build each of my stories from that stuff, and I have to hope it comes across.