what is flushed?

I was reading "Don't be lazy, be consistent: Postgres-R,
a new way to implement Database Replication"
and I found this:

"5.1 General configuration
PostgreSQL uses a force strategy to avoid redo recov­ery,
flushing all dirty buffer pages at the end of each
transaction. With this strategy, response times are
very poor. This makes it difficult to compare with
commercial systems which only flush redo logs to disk.
To allow us to use a more ``realistic'' setting we used
the no­flush option offered by PostgreSQL. With this
option nothing is forced to disk, not even a log record.
This, of course, violates the ACID properties, how­
ever the measured response time was better compara­ble
to standard database systems."

The doc uses Postgresql version 6.4.2.
Has this behaviour been changed?
From the docs of the 7.4 I got that only the redo logs are flushed...

Or am I wrong?