If you'd like to stop Steam from automatically updating a game, select "Only update this game when I launch it" from the game's Library page > Properties > Updates.
So I think in addition to disabling auto-updates you have to play in offline mode once an update happens, or launch outside of Steam. at least, with Skyrim the script extender directly launched the exe so Steam’s “update on launch” wouldn’t happen, and I’m not quite sure what the correct way to do that for Cyberpunk is. 🤔