I don't think they have ulterior motives because I do, I think that because of the loaded language they use (e.g. "taking a stand against AI", "LLM-extrusions") and the dubious reasons they came up with.

It's been decided pretty much everywhere that LLM output is not copyrighted by the LLM vendor. The only realistic risk here is for vibecoded code to be considered public domain, if too little human input was involved, but public domain is functionally equivalent to a very permissive open source license (e.g. MIT minus attribution).