We also had the same issue today (30-9-2020). My colleague and I planned to start a phased release for our app. We double checked everything with multiple people. Everything was correct. And of course we double double checked if we are making use of the phased release option. We can tell you that this option was selected. After going live we noticed that the app was fully released. We are 1000% sure did everything right. We have used safari and Chrome, and on both browsers it occurred. This is the third time we face this issue. We normally do a phased release. Is there a way to prevent this? Is Apple even familiar/aware of this bug?