pg can create duplicated index without any errors even warnning

postgres=# create table t (a int, b int);
CREATE TABLE
postgres=# create index m on t(a);
CREATE INDEX
postgres=# create index m2 on t(a);
CREATE INDEX
postgres=# \d t
Table "demo.t"
Column | Type | Collation | Nullable | Default
--------+---------+-----------+----------+---------
a | integer | | |
b | integer | | |
Indexes:
"m" btree (a)
"m2" btree (a)

is this by design?