for alter user,there is a description:
ALTER USER is now an alias for ALTER ROLE.
so,people will think they are the same.but there are differences:
ALTER USER name SET configuration_parameter { TO | = } { value | DEFAULT }
ALTER USER name SET configuration_parameter FROM CURRENT
ALTER USER name RESET configuration_parameter
ALTER USER name RESET ALL
and
ALTER ROLE name [ IN DATABASE database_name ] SET configuration_parameter { TO | = } { value | DEFAULT } ALTER ROLE name [ IN DATABASE database_name ] SET configuration_parameter FROM CURRENT
ALTER ROLE name [ IN DATABASE database_name ] RESET configuration_parameter
ALTER ROLE name [ IN DATABASE database_name ] RESET ALL
I think we should either metion the differences in doc or make the have no differences. It took some time to find the later today because I most time use alter user and think it equel to alter role.