Why does this install symfony/symfony 2.3.0-RC1 ?

composer.json

{
    "name": "acid/acid",
    "type": "library",
    "description": "Acid Testing Framework",
    "keywords": ["acid", "testing", "framework", "tdd", "xunit", "unit", "dsl", "assert"],
    "homepage": "http://acid.ferm.io/",
    "license": "MIT",
    "authors": [{
        "name": "Pierre Minnieur",
        "email": "pierre@ferm.io",
        "homepage": "http://ferm.io/"
    }],
    "autoload": {
        "psr-0": {
            "Acid\\": "src/"
        }
    },
    "require": {
        "php": "~5.4",
        "andrewsville/php-token-reflection": "1.3.*",
        "henrikbjorn/lurker" : "1.0.*@dev",
        "phpunit/php-invoker": "1.1.*",
        "symfony/class-loader": "2.3.*",
        "symfony/config": "2.3.*",
        "symfony/console": "2.3.*",
        "symfony/debug": "2.3.*",
        "symfony/dependency-injection": "2.3.*",
        "symfony/event-dispatcher": "2.3.*",
        "symfony/filesystem": "2.3.*",
        "symfony/options-resolver": "2.3.*",
        "symfony/process": "2.3.*",
        "symfony/stopwatch": "2.3.*",
        "symfony/yaml": "2.3.*"
    },
    "require-dev": {
        "acid/prophecy": "1.0.*@dev"
    },
    "suggest": {
        "acid/mockery": "Mockery support",
        "acid/prophecy": "Prophecy support",
        "acid/symfony": "Symfony support"
    },
    "bin": [
        "bin/acid"
    ],
    "minimum-stability": "RC",
    "extra": {
        "branch-alias": {
            "dev-master": "1.0.x-dev"
        }
    }
}