This is really no different than if we decided that a dolphin or a naked mole rat are able to hold political rights. If an understanding that this is possible emerges, then as a logical consequence any dolphin or naked mole rat born in US jurisdiction would be a citizen.
Also, it does not say anything about having political rights, just about being a "person", which will surely start a separate debate :)
The rest of the documents are the concurrences (Jackson) and the three, frankly insane, dissents. Thomas's is 90 pages long somehow (I couldn't get through all that one, it's properly crazy).
[1] https://digital.library.unt.edu/ark:/67531/metadc30867/m1/12...
Maybe that’s what they meant, and maybe it’s not.
One thing is sure: depending on which side you are on, it’s “obvious” that it means whatever supports your side.