If you read the documentation for Exporter you'll see that it notes that the :DEFAULT tag is generated from the contents of @EXPORT.

           [!]name         This name only
           [!]:DEFAULT     All names in @EXPORT
           [!]:tag         All names in $EXPORT_TAGS{tag} anonymous li
+st
           [!]/pattern/    All names in @EXPORT and @EXPORT_OK which m
+atch
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Your tag in %EXPORT_TAGS is never seen.