This is the default metaclass implementation that will be used by Object. It is a lowlevel implementation that implements the SMOP OO API HOW part by consulting the REPR API of the given object.
The metaclass is always used just as a responder interface, so there's no much point in having a instance of it. The default is available as the SMOP__MetaClass__Default symbol.
The "metaclass instance" is understood as the use of the metaclass with some object as invocant. It is representation-independent as it uses the REPR API to access the object. The SMOP p6opaque Implementation supports MetaClass definition, and will use it to dispatch the meta calls, and will ask it how to dispatch normal methods.
This is a C3 MI dispatcher that support multi method dispatch and that do the failback to sub dispatch when no method is found.