There's an important distinction here - these ads were impersonating Tom Waits himself. There's something called publicity rights that relates to a person's rig

There's an important distinction here - these ads were impersonating Tom Waits himself. There's something called publicity rights that relates to a person's right to control their public likeness which is presumably what Waits sued over. Here, modders are impersonating a character played by a voice actor and the copyright on the character belongs to the game company, not the actor. Assuming the game company declines to enforce their copyright, it falls back to the actor to enforce their publicity rights. Which I'm not sure they can, since it's not them but rather a character they play. When modders hired soundalikes to extend a character, it was equivalent to finding a similar looking actor. Now, using AI, it's equivalent to using deepfake video. Legally, I assume there's a difference which might be important if the game company decided to sue the modders. But from the perspective of the voice actor, I don't think it matters. Their copyright isn't being infringed.