That was a very simple (but fair) point... So in trying to help others I looked within the GUI for the support Links & noticed the FAQ in the footer.Nobody from Asus will see your question here, let alone answer it. If you really want an answer you'll need to contact Asus.
Curiously I typed in... 160MHz which led me to... How to ensure compatibility of 160MHz and device with RT-AX89X
(Perhaps the info is outdated & definitely not all routers are the same)
But it pointed out something I had never paid much attention to... It suggested having to enable:
(Hmmmmmm... It can't be something that simple, could it?)