Possibly the scenario you describe is the same as in a bug fixed for EA3:
Bug 17601294 - LOW PRIV USER UNABLE TO EXECUTE PACKAGE IN FOREIGN SCHEMA WITH EXECUTE PRIV
A little detail from the test case there (nothing mentioned about Ctrl-F10, however):
1. Create user with ONLY CONNECT, RESOURCE, SELECT_CATALOG_ROLE.
2. Grant EXECUTE on a package in a different schema.
3. Navigate to package in the tree.
4. Execute/Run button is disabled.
Is that close enough?
SQL Developer Team