>> Sorry, I don't understand what I should do in tab-bar-mode
>> for quit-restore-window.  I expected that changes should be
>> in window.el.
>
> Provide an option, say 'tab-bar-save-frame', that allows users to
> customize whether a frame should be deleted when "other tabs are
> available for that frame".  And provide a function, say
> 'tab-bar-save-frame-p', 'window--delete' could call thusly

Ok, here is a better patch: