As we are all AP beta testers, we have seen some of the failures of Tesla's systems, the best example of my point being phantom braking. This is caused by a disagreement between the radar and vision systems. AP is designed to "fail safe", so it brakes until the disagreement is resolved. I understand that Tesla use "whitelists" in their maps as a workaround for this.
The more sensors you introduce, the more overlap you have between them, the higher the probability of disagreement.
Does this make the system safer? You just have to check out the treads about phantom braking to understand how people feel about trusting a nervous ADAS, and how lucky they were that no-one was close enough to rear-end them at the time it happened.
As for Lucid, I imagine they will have to create whitelists for each radar