When running my app in expo go, the app is only semi-locked into portrait. When I rotate the device, the bottom-half of the app animates to landscape, and my bottom navigation labels move to beside the icons. Otherwise, the app stays mostly portrait. Here is the setting I have in app.json:
Hey @blyler, can you share a minimal reproduction case of this that I can run on my end? There is the ScreenOrientation module https://docs.expo.io/versions/v40.0.0/sdk/screen-orientation/ that will take precedence over your app.json configuration but the app should be locked to portrait mode given your current configuration.
Also, can you let me know what device(s) this happens on?