BUG #17827: Rule on insert into table doesn't work when excepting select from the table itself

The following bug has been logged on the website:

Bug reference:      17827
Logged by:          Hanna  Yanchurevich
Email address:      hyanchurevich@spotware.com
PostgreSQL version: 13.2
Operating system:   Centos 7
Description:

To reproduce this bug you may use following script:

create table tbl (id int);
create table rule_stat (msg text, id int);
create rule rule_tbl as on insert to tbl do insert into rule_stat
values('Rule triggered for ',new.id);

insert into tbl 
select 1
except
select id from tbl;

table rule_stat; -- no rows

And using WHERE true clause for target table rule not working too:

insert into tbl 
select 2
except
select id from tbl where true; 

table rule_stat; -- no rows

But using WHERE false clause for target table rule starts working:

insert into tbl 
select 1
except
select id from tbl where false; 

table rule_stat; -- new row appears