According to the docs, it does. It does not work on our side either, so we'll contact Mailchimp to know the reason why it's in the doc.
EDIT: It is indeed not possible, the documentation was outdated. Here is what mailchimp had to say about this:
Hi Philipp,
Thanks for reaching out to MailChimp support with those API concerns, and for allowing us to assist.
With MailChimp version 3.0, users cannot update a subscriber email address. While this may have been available with past versions of our API, it is no longer supported. To update a subscriber email address, the best move will be to manually update from within MailChimp. Each email address is considered to be a unique identifier for list members.
I can certainly understand how the documentation can be a bit misleading, and you do have the ability to update subscriber fields in the list, however email address is not one of them. This is why you have not seen that information updated in MailChimp. I will be reviewing the documentation on this end, and making suggestions to have that article edited if indeed we are suggesting that email addresses can be updated using API. Thanks for this feedback, and for hanging in with us.
We appreciate your time, energy and patience as we reviewed things on our end. Thank you again for choosing MailChimp, and keep us posted with any other questions that you may have moving forward.