Confusing results with lateral references

postgres=# \d t1
      Table "public.t1"
 Column |  Type   | Modifiers
--------+---------+-----------
 val    | integer |
 val2   | integer |

postgres=# \d t2
      Table "public.t2"
 Column |  Type   | Modifiers
--------+---------+-----------
 val    | integer |
 val2   | integer |

There's no data in the table to start with.

postgres=# insert into t1 values (1, 1);
postgres=# insert into t2 values (1, 1), (2, 2);

Session 1
postgres=# begin;
BEGIN
postgres=# update t1 set val = 2 where val2 = 1;
UPDATE 1

Session 2
postgres=# select * from t1, (select distinct val, val2 from t2) t2 where t1.val = t2.val for update of t1;

query waits here because of FOR UPDATE clause

Session 1
postgres=# commit;
COMMIT

Session 2 gives no rows
postgres=# select * from t1, (select distinct val, val2 from t2) t2 where t1.val = t2.val for update of t1;
val | val2 | val | val2
-----+------+-----+------
(0 rows)


Reset values of t1
postgres=# update t1 set val = 1 where val2 = 1;
UPDATE 1

Session 1
postgres=# begin;
BEGIN
postgres=# update t1 set val = 2 where val2 = 1;
UPDATE 1

Session 2
postgres=# select * from t1, lateral (select distinct val, val2 from t2 where t2.val = t1.val) t2 for update of t1;

query waits here

Session 1
postgres=# commit;
COMMIT

AFAIU, both the queries

select * from t1, (select distinct val, val2 from t2) t2 where t1.val = t2.val for update of t1;