Odd/undocumented precedence of concatenation operator

Hi hackers.

Trying to execute the following query on PostgreSQL 9.4.4:

select 'a' >= 'b' || 'c';

Gives the result "falsec", implying that the precedence of the string
concatenation operator is lower than the comparison operator. Changing the
>= into = provides the result false, which is less surprising.

Is this the expected behavior, considering that >= and = behave differently
and that + ranks much higher?

If nothing else, it seems that the concatenation operator should be listed
on the operator precedence table at
http://www.postgresql.org/docs/9.4/static/sql-syntax-lexical.html#SQL-PRECEDENCE-TABLE
?

Thanks!

Shay