Why are you listening to him? He is a random person on the internet.
The train of thought rather usually goes like this: "It is already doable but rather awkward to use. I don't need this feature very often though, and I have more interesting/important things to work on."
The GIMP developers would of course not reject a patch that implemented this in a nice way.
GIMP 2.6 is an important release from a development point of view. It features changes to the user interface addressing some often received complaints, and a tentative integration of GEGL, the graph based image processing library that will eventually bring high bit-depth and non-destructive editing to GIMP.
and goes on with saying that the toolbox menubar has been removed, that the toolbox and docks now are utility windows, that it is now possible to pan beyond the image border, that the freehand select tool has been enhanced to support polygonal selections, and much more."
If you didn't have to work so hard, you'd have more time to be depressed.