out-of-order caution - Mailing list pgsql-hackers

On the docs page for the SELECT statement, there is a caution which
starts with:
| It is possible for a SELECT command using ORDER BY and FOR
| UPDATE/SHARE to return rows out of order. This is because ORDER BY
| is applied first.
Is this risk limited to queries running in READ COMMITTED
transactions?  If so, I think that should be mentioned in the
caution.
-Kevin