They want to confer rights to others that the "owner" does not actually have to confer.
There are several mechanisms under law and treaty that establish rights to those developing a product/work:
And, there are specific mechanisms that cover work not typically eligible for the above three items
4) Granted rights from natural monopolies (e.g. government). Plant protection act, for instance.
And, a special case that is afforded little protection if a knock-off is generated
5) Trade secret
Then there are mechanisms to convey those rights to others
6) Contracts and licenses
For patents, copyright, and trademarks, only one is natural. That is, only one is granted protection upon creation without the need for examination. Copyright.
The various licensing schemes (such as creative commons) are provided to clarify what copyright protections are being retained upon the release of a creative work to the public at large. They are granting certain rights that are naturally owned by the creator to others. You, as the creative individual, receive rights to protect your ownership by default on creation under law and treaty. This is copyright. Registration of copyright is not required, it is natural.
You, as the creator, have produced, 100% of the creative ingredients that the work is using or, in part, contains derived work along with your creative input. If the creative work is a derivative of another creative work, then the appropriate legalize must by in place with the source of the original creator before it is released or risk suffering the consequences. A photo, a written work, music, etc, are considered to have copyright upon creation.
For a seed, you are not granted such a rights by default. Creation of seed, a recipe, ideas, common information, processes, or creations of nature, etc do not fall under copyright. To obtain rights, a breeder, would have to apply for a patent or for other protection mechanisms as provided under law and international treaties. "The Plant Variety Protection Act", for instance. At that point, your intellectual property is safe to be released to the public with an appended license that grants those enumerated rights onto others.
Otherwise, such licensing without a wet signature between parties has little teeth and provides no protection for either the producer or the consumer other than FUD. In fact, such a scheme, can encourage "submarine" attacks on any derivative works developed by both the producers (breeder) and the consumer since the producer is likely unable to ascertain previously protected "breeder work" and likely has not received permission from the original line breeders anyhow. Going all the way back to God (or at least to the legal limits under copyright and patents)...
What is being considered here is a mechanism to protect the financial interests of a breeder while, at the same time, trying to avoid the pain of having to actually apply for formal protection. Or, to develop wet signature contracts. Folk are looking to re-frame the pollination of plants as a creative work with natural rights. Despite the prognostication and feelings, unfortunately, it is not.
I do see the need to encourage good breeders to release good genetics. However, if they are going to go through the trouble and effort to stabilize a strain, then the added effort for formal protection is a small price to pay in that effort. As far as I can tell, applying a license mark to a pack of seed might protect the package design but it will only convey a "desire" in regards to the genetics. They don't actually have the rights that they are trying to convey. However, purposefully stating that genetics are being released into the public domain may help protect against the patenting of derivatives on examination.
Crispr on the hand, well... hmmm.