I know it can seem boring, and I know I go on about it, but PLEASE ensure you fully understand and agree with any contract BEFORE you sign it. If there's anything you don't understand, ask for an explanation. No reputable business will want you to sign a contract you don't understand.
If there's anything you don't like, you can ask for it to be amended. In the case of a contract with the publishers of a womag, the chances of this being agreed to are slim, but you can ask – and if you don't get the response you want you can, and in my opinion should, refuse to sign.
Just a reminder 'All rights' doesn't just mean the magazine can use the story online or in another publication, as well as where it was submitted. Giving up all rights means exactly that. You can't submit the story elsewhere, enter it in a competition, offer it for a charity anthology, publish it eleswhere, not on your blog, or claim ALCS – because those things can only done by the copyright holder. If you've sold all rights, that isn't you. It's no longer your story.
Womags don't need to take all rights. They can offer contracts which give them the right to use the story when and where they wish, yet allowing the author to also re-use their story once it has been published and any exclusivity period has passed. This is what most of them currently do, at least for most of their authors. I've heard of new (to them) authors being offered only all rights contracts. You can imagine what might happen if some of those are signed.
UPDATE – I've had a response from ACLS. "If you don’t hold copyright, you need to have an agreement in place with your publisher in order to claim. ALCS does not pay out to publishers (they claim through @PLSlicensing) so if they hold the rights, they can’t claim for the article through us."
They provide more information on copyright here.