log_statement and PREPARE

The docs (8.1) say the following about log_statement:

-- snip --
... mod logs all ddl statements, plus INSERT, UPDATE, DELETE, TRUNCATE,
and COPY FROM. PREPARE and EXPLAIN ANALYZE statements are also logged if
their contained command is of an appropriate type.
-- snip --

Can someone please expain the meaning of, "if their contained command is
of an appropriate type"? I take it to mean that the prepared statement
will be logged if the it contains an INSERT (if 'mod' was chosen, of
course).

I ask because i've set log_statement to 'mod' but am not seeing any of
my prepared statements in the log. INSERT, UPDATE, and friends i do see.

FWIW, the app is PHP using MDB2. But checking its source doesn't give me
any reason to believe the issue lies there. Shouldn't i see these PREPAREs?

brian