BUG #8681: column 'n_tup_del' of pg_stat_user_tables doesn't change in case of truncate

The following bug has been logged on the website:

Bug reference: 8681
Logged by: Anit chakkarwar
Email address: anitchakkarwar(at)gmail(dot)com
PostgreSQL version: 9.3.1
Operating system: Linux
Description:

I came across one issue while truncating table in Postgres9.3, please find
below steps:

First Scenario:

1. Create table and insert some rows.
2. Now delete two rows.
3. If I delete rows 'n_tup_del' column in pg_stat_user_tables is set 2.
4. Do vacuum now i.e vacuum table <tablename>
5. 'n_tup_del' column in pg_stat_user_tables is still showing 2 records.

Second Scenario:

1. Create table and insert some rows.
2. Now truncate table.
3. n_tup_del column in pg_stat_user_tables is 0.

If I do truncate then n_tup_del value is 0 but all the rows are deleted from
table.

Is this something expected behaviour ?