Hi,
I'm a user with accessibility needs that require reduced motion in my interfaces. Website toolbars that auto-hide on scroll usually handle the reduced-motion preference by foregoing their slide transitions and just disappearing/reappearing instantly.
The auto-hiding navigation/address bar should do this too, in response to the Android system "disable animations" setting. The conditions for hide/unhide should remain the same.
I don't know what the iOS equivalent to this tweak would be, so I can't offer advice on that. But this behavior should be available to everyone who needs reduced motion.