You are right, but this is easy to solve. The less nice solution is to show a little explanation before locking the device, the better one depends on OSes. They

You are right, but this is easy to solve. The less nice solution is to show a little explanation before locking the device, the better one depends on OSes. They should simply provide a way for devs to trigger the lock screen for this specific purpouse and let devs specify a message, color scheme, theme, logo, whatever that needs to feel the lock mechanism more integrated in the app.