There is nothing about your "otherwise it is considered as the value" version in ApiDocs (http://api.symfony.com/2.4/Symfony/Component/OptionsResolver/OptionsResolverInterface.html#method_setNormalizers):

Sets normalizers that are applied on resolved options.
The normalizers should be closures with the following signature:
function (Options $options, $value)
The second parameter passed to the closure is the value of the option.
The closure should return the normalized value.

Nothing about "one-argument" form.

But we can wait 2 month more. Maybe it appears.