I’ve looked all over and can’t find the option that governs what happens to the overall Scrivener window when I close or open the binder or inspector. I know I can change the behavior with the Option key, but I don’t want to have to press that key each time. Pretty sure the behavior changed without my input.
It could be, I suppose. I think (don’t know) that the preferences are upgraded in this update for the new features and this may be an unintended consequence of that.
No, that option has been un-checked by default since 3.0 (when it was introduced). This option won’t have been affected by the update unless your Preferences were entirely reset.