Observe the warnings generated here:
The private var feature CLJS-1702 already supports instrumentation of private vars (albeit where the specs are being constructed in that private namespace, just enabled from another). The above case is perhaps a mild extension to it and it is debatable as to whether a diagnostic should be emitted.
We have a case here, where this is done in core (it only affects self-hosted), so if this ticket is not addressed perhaps we should address that case. https://github.com/clojure/clojurescript/blob/0773689ec748109a8c09ba924f90c25875eb6a9d/src/main/cljs/cljs/core/specs/alpha.cljc#L201