BUG #18320: Duplicate primary key records in table

The following bug has been logged on the website:

Bug reference:      18320
Logged by:          vishnu ch
Email address:      jaihind213@gmail.com
PostgreSQL version: 15.2
Operating system:   aarch64-apple-darwin21.6.0
Description:

hi
i create table with primary key and inserted a few records but i am
surprised to see duplicate records having same primary key ?
is this a bug ? or am i missing something in postgres ?

i noticed other conversations/bugs like BUG #16938
---------------------
1. create table
CREATE TABLE foo (
    id integer PRIMARY KEY,
    name VARCHAR(255) NOT NULL
);

2. insert records:
insert into foo values (4, 'boo');
insert into foo values (6, 'asd');
insert into foo values (6, 'asd');
.....

3. select * from foo;

id|name|
--+----+
 6|xxx |
 5|yyy |
 5|yyy |
 6|xxx |
 4|boo |
 6|asd |
 6|asd |
 6|asd |
 4|boo |

---------------------------------------
Other details:
1. PostgreSQL 15.2 on aarch64-apple-darwin21.6.0, compiled by Apple clang
version 14.0.0 (clang-1400.0.29.102), 64-bit
2. Using https://postgresapp.com/ to launch postgres 15 on mac m1 - macOs
Monterey