According to http://dev.mysql.com/doc/refman/5.1/en/replication-formats.html :
Replication capabilities in MySQL originally were based on propagation
of SQL statements from master to slave. This is called statement-based
replication (often abbreviated as SBR), which corresponds to the
standard statement-based binary logging format. In MySQL 5.1.4 and
earlier, binary logging and replication used this format exclusively.
Row-based binary logging logs changes in individual table rows. When
used with MySQL replication, this is known as row-based replication
(often abbreviated as RBR). In row-based replication, the master
writes events to the binary log that indicate how individual table
rows are changed.
As of MySQL 5.1.8, the server can change the binary logging format in
real time according to the type of event using mixed-format logging.
When the mixed format is in effect, statement-based logging is used by
default, but automatically switches to row-based logging in particular
cases as described later. Replication using the mixed format is often
referred to as mixed-based replication or mixed-format replication.
For more information, see Section 126.96.36.199, “Mixed Binary Logging
From MySQL 5.1.12 to MySQL 5.1.28, mixed format is the default.
Beginning with MySQL 5.1.29, statement-based format is the default.
Based on this excerpt and the fact that MySQL 5.1.30 was the very first GA release of MySQL 5.1, MySQL 5.1.41 has to have row-based binary logging, and thus row-based replication.