Boolean Implicitly Typed?

Good day,

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

Don't the boolean values true and false qualify as an implicitly typed
constants as well, as they don'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Is this documentation just out of date, or am I not quite grasping the
specific connotation of 'implicitly typed' constants? Thoughts? ;)

Regards,
Jw.
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