`read-from-minibuffer' seems to always return a multibyte string, but why?

I ran M-x ielm, executed

(set-buffer-multibyte nil)
(read-from-minibuffer "Input: ")

and got a multibyte string back.

The manual says: "If the argument inherit-input-method is non-nil, then
the minibuffer inherits the current input method (see Input Methods) and
the setting of enable-multibyte-characters (see Text Representations)
from whichever buffer was current before entering the minibuffer". By
this logic, I probably should have been given a unibyte string back
instead. Is this a contradiction?

The manual merely says that either a STRING (which one? Uni- or multi-?)
or a Lisp object is returned.

By the way, a multibyte string was really what I wanted out of this. I
just want to be sure that this behavior is not accidental.

It feels like I am missing something obvious.


Many thanks.