>> This is a feature: it allows you to scroll through the text shown in
>> the minibuffer, in case you want to edit it. Use M-p to go directly
>> to the previous history.
>
> I understand it's a feature, but as you see in the picture the prompt is
> empty, and the full default replacement is visible.
>
> In this case arrow should retrieve the previous history, instead of going
> into the prompt, because there is nothing to scroll.

Thanks for the well justified request.  This patch avoids moving point
to the prompt on the rightful assumption that most of the time the users
would not want to edit read-only text: