Missing (?) supportedDestinations deploymentTarget #1577

First time trying to use supportedDestinations. This configuration in project.yml

targets:
  AppName:
    type: application
    platform: auto
    supportedDestinations: [macOS, iOS]
    deploymentTarget:
      macOS: 15.0
      iOS: 18.0
    dependencies:
      ...

Does not set any deployment targets in the generated pbxproj file. When I open the generated project in Xcode (testing with Xcode 26) the deployment target for both macOS and iOS are set to 26, not the desired values.

Am I doing something wrong? Is this a limitation of supportedDestinations? I've tried it both with and without setting platform: auto. No difference.