test commit_delay

I am trying to see the impact of commit_delay.
Set it to 100000 (microseconds), i.e. to 100ms
synchronous_commit is kept to default (i.e. ON)

Now I expect my DML statements to take atleast 100ms. But when I try to execute a few and measure using the timing command of postgres or the time command of linux, the duration is just a few milliseconds.
time /usr/local/pgsql/bin/psql -c "insert into abc values(1);" test
INSERT 0 1
real    0m0.010s

user    0m0.000s
sys     0m0.000s

OR

test=# \timing
Timing is on.
test=# insert into abc values(1);
INSERT 0 1
Time: 2.637 ms

What am I doing wrong ?

Thanks.