The statistics provided by this module are not stored in CDB (when the callpoint is annotated), but by a ConfD-internal data provider (i.e. it counts the packets etc and provides the counters when requested). You can read them programmatically via the MAAPI api (which of course works also for any data stored in CDB, whether config or state, and is the equivalent of how it is read from a NB interface).
If you compile the module without a callpoint annotated, the storage for config false data will indeed default to CDB-operational - but this doesn’t work, since there isn’t any code to update that data (unless you (reduntantly) write it, but I don’t where you would get the data from in that case).
Bottom line, many of the YANG modules provided as source in $CONFD_DIR/src/confd/yang must be compiled with the corresponding annotation modules in order to actually “work” - this just amounts to connecting the data model to the instrumentation, like you may do for your “own” modules - the difference is that the instrumentation is internal to ConfD in these cases.