I run the command eval-print-last-sexp with C-j, it prints "t", the default value.
------------------ ???????? ------------------
??????: "Eli Zaretskii"<eliz@gnu.org>;
????????: 2019??9??25??(??????) ????1:17
??????: "Juanma Barranquero"<lekktu@gmail.com>;
????: "Albert"<georgealbert@qq.com>;"37495"<37495@debbugs.gnu.org>;
????: Re: bug#37495: 27.0.50; lwindow doesn't pass to system
> From: Juanma Barranquero <lekktu@gmail.com>
> Date: Tue, 24 Sep 2019 18:55:00 +0200
> Cc: georgealbert@qq.com, 37495@debbugs.gnu.org
>
> But then, he says "Iwindow key with the default setting(nil)". But w32-pass-lwindow-to-system's default value
> is t, both in 26.2 and 27.0.50.
I didn't see the "nil" part in the original report, just the "with the
default setting" part.