When I run "emacs -Q -l the-following-snippet.el",

--8<---------------cut here---------------start------------->8---
;; this snippet does provoke the bug.
(set-face-attribute 'default nil :weight 'medium)
(menu-bar-mode 0)
--8<---------------cut here---------------end--------------->8---

I find an Emacs frame with bad initial rendering: There is no text
visible. See attached screenshot.

When I resize the frame, the rendering is corrected, i.e. the text of
the scratch buffer becomes visible.

The bug IS ALSO provoked when the first S-expressions is replaced with
one of the following:

--8<---------------cut here---------------start------------->8---
;; either
(custom-set-faces '(default ((t :weight medium)) t))
;; or
(custom-set-faces '(default ((t :height 110)) t))
;; or
(custom-theme-set-faces 'user '(default ((t :slant italic)) t))
;; or similar.
--8<---------------cut here---------------end--------------->8---

The bug IS NOT provoked when the order of the two S-expressions is
reversed, for example:

--8<---------------cut here---------------start------------->8---
;; this snippet does not provoke the bug.
(menu-bar-mode 0)
(set-face-attribute 'default nil :weight 'medium)
--8<---------------cut here---------------end--------------->8---

The bug IS NOT provoked when any face other than "default" is altered,
for example:

--8<---------------cut here---------------start------------->8---
;; this snippet does not provoke the bug.
(set-face-attribute 'link nil :weight 'medium)
(menu-bar-mode 0)
--8<---------------cut here---------------end--------------->8---

The bug IS NOT provoked for some face-attributes, e.g. ":box" and
":underline":

--8<---------------cut here---------------start------------->8---
;; this snippet does not provoke the bug.
(set-face-attribute 'default nil :box t)
(menu-bar-mode 0)
--8<---------------cut here---------------end--------------->8---

The person with nickname "twb" in #emacs on irc.libera.chat suggests
"there is just a 'and then rerender' command missing somewhere".
Personally, I wonder if there is a mistake how menu-bar.el handles
a customized default face. See:

https://git.savannah.gnu.org/cgit/emacs.git/tree/lisp/menu-bar.el?h=e4e1e268c8e9f7de6fe5d4b05beb595a1781c02c#n839