Further comment on your feeling that you don’t remember previously having to have something selected when assigning the shortcut.
I just tried it again in SU 2014. No group or component selection, no Explode in the context menu - you don’t get it when you select raw geometry.
No selection, no Explode command in the Shortcuts lists.
It’s always been that way AFAIK. So probably your recollection is a false memory - we all get them at some time.