After selecting a primitive on a geometry and transforming it (in Edit SOP), you can grow selection using Shift+G , but it doesn't shrink it by pressing Shift+S, is this a bug?
Shift+S is bound to straighten selection in the Edit state, which overrides the shrink selection binding. I'd argue that it's a bug because you can't even use the RMB > Select > Shrink Selection menu entry to do it because of this conflict.