I am curious to know if in the state of California if this is correct: if the deceased owned life insurance and nominated a beneficiary of the policy, the proceeds of that policy would not pass into the deceased's estate, but would go directly to the nominated beneficiary.

In every state I know of or have worked in the insurance industry, if there is a beneficiary and that beneficiary is alive the money goes directly to them and does not go into the estate.

There can of course be exceptions
For example if a child support order stated that the parent has to have a policy on a child.
But they don't , the other parent could put a claim against the policy because it was ordered to name the child as a beneficairy but they did not.

*** this is a real case going on right now. Not sure how the court will rule on it.

But unless there is a claim or law suit against the policy it will not go into probate