Why shouldn't they? I think it's ridiculous to be able to review something which you have not experienced and I don't see a good reason why they should be allowed. The lockout should be until at least one person (ideally more) have experienced the fully released product.

Authors and publishers ship pre-release advance copies to popular reviewers, as part a part of the promotion leading up to launch, like movies do with prescreenings. Goodreads is notorious for having these types of reviewers, in fact, it's one of the carrots that serial reviewers go after.

This book is still in editing, though. It isn't even available as a pre-release review copy at all yet.

I mean, this is assuming that pre-release reviews are from advance copies, not WIP.