Can you release to Public Domain & still retain copyrights?

Intel says it did

[john_k]

This disclaimer is at the top of the specifications for the DCX 1.2 file format:

This specification was jointly developed by Digital Communications
Associates, Incorporated and Intel Corporation. Although it has been
released into the public domain and is not confidential or proprietary, the
specification is still the copyright and property of Digital Communications
Associates, Incorporated and Intel Corporation.

Does it make sense that they have released the specification into the public domain, yet they claim to retain copyrights? I thought the two were mutually exclusive.

[john_k]

After pondering this a little more, the best I can make of it is that they want to allow anyone to utilize the specification (i.e. no royalties or patent litigation as with GIF and JPG). But they retain the right to publish the specification and thereby maintain control over changes to it.