Intention was that each debug & each release variant has it's own signing key (4 variants -> 4 signing keys), no signing with default key. But this doesn't work

wrong_build.gradle

...

signingConfigs {

    // debug config is intentionally deleted in favor of debugBlue & debugRed

    debugBlue {
        storeFile file(debugBlueKeystore)
    }
    debugRed {
        storeFile file(debugRedKeystore)
    }

    releaseBlue {
        storeFile file(releaseBlueKeystore)
        storePassword 'release_blue_pass'
        keyAlias 'release_blue_alias'
        keyPassword 'release_blue_pass'
    }
    releaseRed {
        storeFile file(releaseRedKeystore)
        storePassword 'release_red_pass'
        keyAlias 'release_red_alias'
        keyPassword 'release_red_pass'
    }
}

productFlavors {
    blue {
          applicationId 'com.sample.blue'
          versionCode 1
          versionName 'blue-1'
    }

    red  {
          applicationId 'com.sample.red'
          versionCode 1
          versionName 'red-1'
    }
}

buildTypes {
        debug {
            versionNameSuffix "-debug"

            productFlavors.blue.signingConfig signingConfigs.debugBlue
            productFlavors.red.signingConfig signingConfigs.debugRed
        }
        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
            zipAlignEnabled true

            productFlavors.blue.signingConfig signingConfigs.releaseBlue
            productFlavors.red.signingConfig signingConfigs.releaseRed
        }
}
...

I expected that ./gradlew signingReport gives defined signatures for debug builds (debugBlueKeystore, debugRedKeystore),
but these builds are signed with same (system default) keystore saved in /Users/someUser/.android/debug.keystore on MacOS

Not sure where this default 'debug' config is coming from.. :S

----------
Variant: blueDebug
Config: debug
Store: /Users/someUser/.android/debug.keystore
Alias: AndroidDebugKey
...
----------
Variant: redDebug
Config: debug
Store: /Users/someUser/.android/debug.keystore
Alias: AndroidDebugKey
...
----------
Variant: blueRelease
Config: releaseBlue
Store: releaseBlueKeystore
Alias: release_blue_alias
...
----------
Variant: redRelease
Config: releaseRed
Store: releaseRedKeystore
Alias: release_red_alias
...
----------