Hint BNL() doesn't work when join_cache_level>= 5 or join_cache_hashed=off

CREATE TABLE t10(a INT);

INSERT INTO t10 VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);

CREATE TABLE t12(a INT, b INT);

INSERT INTO t12 SELECT a,a from t10;

CREATE TABLE t13(a INT, b INT, c INT, filler CHAR(100), key (a,b));

INSERT INTO t13 select a,a,a, 'filler-data' FROM t10;

set optimizer_switch= 'join_cache_hashed=on,join_cache_bka=on,mrr=on';

set join_cache_level = 3;

EXPLAIN  SELECT * FROM t12, t13

  WHERE t12.a=t13.a AND (t13.b+1 <= t12.b+1);

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t12	ALL	NULL	NULL	NULL	NULL	10	Using where

1	SIMPLE	t13	hash_ALL	a	#hash#a	5	test.t12.a	10	Using where; Using join buffer (flat, BNLH join)

set join_cache_level = 5;

EXPLAIN  SELECT /*+ BNL() */ * FROM t12, t13

  WHERE t12.a=t13.a AND (t13.b+1 <= t12.b+1);

id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra

1	SIMPLE	t12	ALL	NULL	NULL	NULL	NULL	10	Using where

1	SIMPLE	t13	ref	a	a	5	test.t12.a	1	Using index condition(BKA); Using join buffer (flat, BKA join); Rowid-ordered scan