That doesn’t apply here. Claude code is what leaked, not the models. Anthropic definitely owns Claude code copyright and can DMCA without it being contradictory
But even that is vague and possibly not true. If they used LLM's to generate all of the code, then it may not fall under copyright, by the requirement of human authorship (which for code I think has not been tested yet in court) [1].
Its unclear whether there is sufficient human authorship in cc for copyright to stick on a court. Anthropics arguments would hinge on the curation of plans and the direction decisions, which haven't been properly tested as the source of authorship yet. Typically contracted implementers sign over copyright to the project owners, and this is where there is case law.
Something that was meant to remain secret made public, is not the same thing as whether something public is public.
If anything, this is a question of whether you owe royalties to the owner of IP you consumed in your life since it became part of and trained your mind, identity, and outputs too.
According to IP owners ever since things were digitized, you technically own nothing and simply paid for an authorization to use any given IP for the duration that the IP owner authorized you to use it and you continue to pay, so pay your monthly meat-AI bill to pay for all the IP your mind has been trained on.
[1] https://www.congress.gov/crs-product/LSB10922