Can't install a package from VCS repository that requires another package that is also from VCS repository

[javaDeveloperKid]

Both packages exist on satis and releases section contains branch task-123.
In my application root I run:

$ composer require vendor/package-a:dev-task-123 as 1.0
Problem 1:
  - vendor/package-a dev-task-123 requires vendor/package-b task-123 -> no matching package found.

Main composer.json:

{
  "repositories": [
    {
      "type": "composer",
      "url": "https://satis.example.com"
    }
  ]
}

Package A composer.json:

{
  "repositories": [
    {
      "type": "composer",
      "url": "https://satis.example.com"
    }
  ]
  "require": {
    "vendor/package-b": "dev-task-123 as 1.0"
  }
}

[fredden]

"repositories" is only read for the root package, so that doesn't seem relevant here. is this perhaps a minimum-stability issue? Does this work when set to dev?

[javaDeveloperKid]

Weird thing is that it works when I require both package-a and package-b in the root composer.json.