Inconsistency of using parameter data types

WITH data_types AS (SELECT specific_schema, specific_name,
regexp_replace(specific_name,'_[0-9]*$','') AS routine_name, 
pg_get_function_identity_arguments(translate(substring(specific_name,'_[0-9]+$'),'_','')::int::oid) AS parameters,
parameter_name, 
CASE WHEN data_type='numeric' THEN data_type || '(' || numeric_precision || ',' || numeric_scale || ')'
WHEN character_maximum_length IS NOT NULL THEN data_type || '(' ||  character_maximum_length || ')'
WHEN datetime_precision IS NOT NULL AND data_type<>'date' THEN data_type || '(' ||  datetime_precision || ')'
ELSE data_type END AS data_type
FROM INFORMATION_SCHEMA.parameters
WHERE  regexp_replace(specific_name,'_[0-9]*$','') NOT IN ('f_assume_you_must_use_files', 'f_check_format_comma_separated_list', 'f_check_password', 'f_default_value_with_no_match') AND 
specific_schema NOT IN (SELECT schema_name
FROM INFORMATION_SCHEMA.schemata
WHERE schema_name<>'public' AND
schema_owner='postgres' AND schema_name IS NOT NULL) AND NOT EXISTS (SELECT 1
FROM pg_catalog.pg_depend d inner join pg_catalog.pg_proc pc ON d.objid=pc.oid
WHERE EXISTS (SELECT 1 FROM pg_catalog.pg_extension e WHERE d.refobjid=e.oid) AND
pc.proname || '_' || pc.oid = parameters.specific_name))
SELECT parameter_name, string_agg(specific_schema ||'.'|| routine_name  || '(' || parameters || ')' || ' ' || Upper(data_type),';<br>' ORDER BY data_type, specific_schema, specific_name) AS types
FROM data_types AS dt
WHERE EXISTS (SELECT 1 FROM data_types AS dt2 WHERE dt.routine_name<>dt2.routine_name AND dt.parameter_name=dt2.parameter_name
AND dt.data_type<>dt2.data_type)
GROUP BY parameter_name
ORDER BY parameter_name;