Boolean Constants Implicit?

Good day,

The on-line documentation lists that PostgreSQL supports only four
implicitly typed constants: string, bit string, integer and floating
point.

Doesn't boolean (true/false) qualify as an implicitly typed as well, as
it doesn't need to be bound by single quotes? For example:

lx=# SELECT true AS bool_const_t, false AS bool_const_f;
bool_const_t | bool_const_f
--------------+--------------
t | f
(1 row)

lx=#

Is this documentation just out of date? Thoughts? ;)

Regards,
Jw.
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