ORA-01450 while indexing 12c extended type

SQL> create table t32k
  2  (
  3     ve   varchar2 (32767)
  4  )
  5  tablespace users;

Table created.

SQL> select block_size from dba_tablespaces where tablespace_name = 'USERS';

BLOCK_SIZE
----------
      8192

SQL> create index t32k_idx on t32k ( ve );
create index t32k_idx on t32k ( ve )
                         *
ERROR at line 1:
ORA-01450: maximum key length (6398) exceeded

The ORA-01450 is the expected, documented behavior.