This feature could precisely fit a polygonal selection or could allow to expand the feathered selecton over the edge of the convas for example.
Yes, this is missing for bitmap selections. However, if you convert a selection to vector, you can already move the selection using the shape tool (white arrow, top-left in toolbox)
Right now, if you make the global selection visible, you can move it around with the move tool, but it's still not an ideal workflow.
That's what we have for now, resolving as later. If we want to work on this, we need a solid interaction design. WISHGROUP: Needs proposal and design