must synchronous_standby_names be set?

I'm testing synchronous replication on 9.2devel - both instances are on a single machine.

The primary shows synchronous_commit = on
and synchronous_standby_names = ''.

The standby receives updates fine.

Now, does the 'synchronous_commit = on' absolutely mean that the session is sync-replicating? 
Could it be non-synchronously replicating?

If so, this information in the manual seems wrong:

"
25.2.6.1. Basic Configuration

Once streaming replication has been configured, configuring synchronous replication requires only
one additional configuration step: synchronous_standby_names must be set to a non-empty value.
"
( the 'must be set' part )


Two questions:

1. How to query a session to make absolutely sure that replication is actually synchronous?

2. Does sync-repl really need synchronous_standby_names to be set?



Thank you,

Erik Rijkers