I don't want to defend Discord, but that's just not true. That announcement did not say all processing would be on-device, only when you use the face scan.

> Video selfies for facial age estimation never leave a user’s device

> Facial scans never leave your device. Discord and our vendor partners never receive it.

Meanwhile they're also clear that uploaded IDs do get sent to "partners":

> Quick deletion: Identity documents submitted to our vendor partners are deleted quickly— in most cases, immediately after age confirmation.