[plt-scheme] eq-hash-code

The documentation says:
"Returns an exact integer; for any two eq? values, the returned
integer is the same. Furthermore, for the result integer k and any
other exact integer j, (= k j) implies (eq? k j)."

But it is always true that (= k j) implies (eq? k j) purely by
definition of = and eq?.  So this statement appears to say nothing
useful.

What is really meant here?

--Mark