Firebase app distribution violating google play policy

I’ve been using firebase app distribution since over a year for a closed testing app on the play store. I suddenly received a suspension warning for the following reason :

Device and Network Abuse policy: Violation of Device and Network Abuse policy. For example, your app is using the firebase apkupdater SDK or library, which causes users to download or install applications from unknown sources outside of Google Play.

The only code I have for my test app is :

val firebaseAppDistribution = FirebaseAppDistribution.getInstance()
firebaseAppDistribution.updateIfNewReleaseAvailable()
    .addOnProgressListener {
        // (Optional) Implement custom progress updates in addition to
        // automatic NotificationManager updates.
    }
    .addOnFailureListener { e ->
        // (Optional) Handle errors.
        if (e is FirebaseAppDistributionException) {
            when (e.errorCode) {
                FirebaseAppDistributionException.Status.NOT_IMPLEMENTED -> {
                    // SDK did nothing. This is expected when building for Play.
                }
                else -> {
                    // Handle other errors.
                }
            }
        }
    }

I tried to make appeal but the pre-generated response didn’t help at all. Is there something I did not understand with the app distribution?