I tried to replicate the issue in a small setup, but the results looks as expected:
(pc/defresolver inner-call [{:keys [parser] :as env} _]
{::pc/output [:inner-result]}
{:inner-result (parser env [{[:foo 1] [:foo]}])})
;; define a list will our resolvers
(def my-resolvers [inner-call])
;; setup for a given connect system
(def parser
(p/parser
{::p/env {::p/reader [p/map-reader
pc/reader2
pc/open-ident-reader
p/env-placeholder-reader]
::p/placeholder-prefixes #{">"}}
::p/mutate pc/mutate
::p/plugins [(pc/connect-plugin {::pc/register my-resolvers})
p/error-handler-plugin
p/request-cache-plugin
p/trace-plugin]}))
(comment
(parser {} [:inner-result]))