Valve's disclosure policy is very specific. It's about visual assets (models and textures), audio (music and VA), script writing (not explicitly translation or subtitling either), and that's it. There is no requirement to disclose AI-assisted, AI-researched, or fully AI-generated code.

The assets stuff also is specifically about the final game. If a studio uses AI for placeholders and doesn't ship them in the actual Steam game, it's not required to disclose that process.