> From: Takesi Ayanokoji <ayanokoji.takesi@gmail.com>
> Date: Sun, 5 Jan 2020 01:47:41 +0900
>
> Some parameters are only meaningful for frames on certain kinds of display (@pxref{Frames}).  If @var{alist}
> includes parameters that are not meaningful for the @var{frame}'s display, this function will change its value
> in the frame's parameter list, but will otherwise ignore it.
> ---
>
> So, my question is,
> Either 'not' or 'otherwise' is not necessary, isn't it?

No, both are necessary.  The "otherwise" part means "other than
changing the value of the parameter".