There is no
getKeys() method in the cachefactory so I’m not sure what you’re seeing. CacheBox does not store keys directory-- it is a cache aggregator that can have any number of named caches, each using different cache providers (in memory, memcached, redis, etc) To see the keys in a given cache, you’d need to first get the cache in question and then ask for the keys.
cachebox.getCache( 'default' ).getKeys()
Now that said, none of what I just said has anything to do with your original question. Singletons are a concern of WireBox, not CacheBox. If you want to see all the singletons in WireBox, you need to access the singleton scope and look at its contents.
wirebox.getScope( 'singleton' ).getSingletons().keyArray()