Ahh-- of course. I didn’t even notice that the OP was talking about singletons. Yep, WireBox will only use CacheBox if you are actually persisting the object in a cache.
Dump the object and you will see the methods to interact with the singleton scope.
Also, you can listen to the debugger interception points: afterDebuggerPanel and beforeDebuggerPanel and actually send your own panel to the debugger. So you can build a singleton viewer if needed.