TTL does not compact rows

I find that the rows are not compacted when gc_grace_seconds is set through alter table command. Following were the steps performed:

1. Created the following table:
CREATE COLUMNFAMILY MirrorSmokeTest (
id uuid PRIMARY KEY,
test_message varchar
);

2. Ran an alter command:
alter table MirrorSmokeTest WITH gc_grace_seconds = 60;

3. Insert a row into the above table:
insert into MirrorSmokeTest (id, test_message) Values ('4a7fad82-8298-4d91-85de-8255b7c7e4f5', '2') USING ttl 60;

4. Waited for 60 seconds and ran a query that results in the following output:

select * from MirrorSmokeTest;
id
--------------------------------------
4a7fad82-8298-4d91-85de-8255b7c7e4f5

5. Ran a flush and compact and reran the query that results in the following:

select * from MirrorSmokeTest;
id
--------------------------------------
4a7fad82-8298-4d91-85de-8255b7c7e4f5