But let's take your scenario: even if you only showed me it's not behind one of your doors, I still know that there's a 9/10 chance it's behind one of the remai

But let's take your scenario: even if you only showed me it's not behind one of your doors, I still know that there's a 9/10 chance it's behind one of the remaining 8 doors. This still gives each of your doors a better chance than the door I initially picked, and I should still switch to one of them.