TestFlight: My build is immediately available to internal testers. Why might this be?

I have a React Native app on TestFlight. In the past I've always had to wait about 12 hours for the TestFlight build to be approved, and then its status shows as Testing or Approved. With the app I'm working on now, its status is just Ready To Submit and it was available for Internal Testers immediately. Does anyone know what the difference between these two scenarios is? The reason I'm wondering is that the build available to internal testers now is behaving differently than I expected it too, and in order to troubleshoot this I want to know if this immediately-available Ready To Submit type of build is expected to behave differently than other builds.