I would think that hotels/casinos would be far more likely to employ detection dogs rather than metal detectors that are going to be hitting so many false positives to be useless or calibrated so low that they’re equally likely to miss a threat.
Whether or not the measures would have prevented a mass shooting is impossible to say but the point is Wynn actually did, over a year before, go on record as saying LV was a target city and he was employing hightened security at his hotels. He was dismissed as being ‘obsessed’ by other casino operators. So now he does technically sit on high enough ground to criticize them and say I told you so.