BUG #16072: Two transaction to delete all data, The result is not hopeful

The following bug has been logged on the website:

Bug reference:      16072
Logged by:          qiangwei zhu
Email address:      zhuqiangwei010@hotmail.com
PostgreSQL version: 10.5
Operating system:   "PostgreSQL 10.5 on x86_64-pc-linux-gnu, compiled
Description:

my test table struct is:
create table test(
  f1 int
)

test table data is:
f1
---------------
1
1
1
1
1

I open two query analyzer,
trans A:

begin TRANSACTION;
delete from test;
INSERT into test(f1)
values(1)


trans B:
begin TRANSACTION;
delete from test;

then commit transA, last commit transB

why in test table has 1 rows at last?
sqlserver 、oracle、mysql database，use same test solution, there was no data
in test table at last.