Can a district attorney in his opening statement say that nothing he said could be considered as evidence?

The district attorney in his opening statement said, and the court instructed, that nothing he said in his opening statement could be considered as evidence. No showing of bad faith was made here. See People v. Williams (1962) 202 Cal.App.2d 387, 397, 20 Cal.Rptr. 740, 747, where the court said: 'In the present case, the defendant made no objection to the statement of the district attorney and if he knew such statement could not be proven, should have objected at the time instead of relying on the possibility of a later reversal.'