TARGETED_DEVICE_FAMILY set to 1,2 when specified 1

This doesn't work:

settings:
  base:
    CLIENT: XXX
    IPHONEOS_DEPLOYMENT_TARGET: '15,0'
    SWIFT_VERSION: '5.7'
    TARGETED_DEVICE_FAMILY: 1
  configs:
    Debug:
      GCC_C_LANGUAGE_STANDARD: gnu99
      SDKROOT: iphoneos
      SWIFT_ACTIVE_COMPILATION_CONDITIONS: DEBUG
      SERVER: DEV
    Fastlane:
      SDKROOT: iphoneos
      SERVER: PROD
    Release:
      SDKROOT: iphoneos
      SERVER: PROD
      
targets:
  ContentApp:
    templates:
      - Scripts
      - DefaulConfig
    dependencies:
      - sdk: Foundation.framework
    platform: iOS
    type: application
    settings:
      base:
        PRODUCT_NAME: XXX
        PRODUCT_BUNDLE_IDENTIFIER: com.xxx.$(CLIENT)

If I move the TARGETED_DEVICE_FAMILY into the Targets settings:base it works like expected..
my understanding is that the settings should be additive.. so if nothing is in the Target group it should take from the settings at top

Start by reproducing the reported YAML configuration and compare the generated Xcode project when TARGETED_DEVICE_FAMILY is under settings.base versus targets.ContentApp.settings.base. Trace how settings are inherited or merged, then verify that the target receives the top-level value when it does not define one itself.