Have we confirmed that this alert included only the link to Xhitter, without the other data?

I guess you're looking for another source, but as far as this one goes it states in the first paragraph that this was exactly the problem:

Earlier this week, the California Highway Patrol sent an Amber Alert push notification to phones in the Los Angeles area about a 14-year-old girl that authorities believed had been abducted. But instead of conveying vital information that could help locate the victim within the notification itself, the law enforcement agency linked to a post from its official X account, a practice it adopted six years ago. But this time, many people reported they could not view the alert because they hit a screen that prevents users from seeing any content on X until they sign into their account.