Can an employer pick and choose who gets the opportunity for voluntary time off? Please see details for more info.?

This does not involve me, but from the outside looking in, it's a questionable situation. They have a team who comes in 30 minutes early to prep the building and are saying "it is a privilege" to be on this team so they do not have to offer VTO on days that it's available to those who come in 30 minutes later (which is about every single day) and work the same shift duration (early team is 10-2 and everyone else 10:30-2:30). Is this fair game? I don't understand how these people don't have the same opportunity at a free day off as others. My main concern is for those who work second jobs with a different employer such as second shift (3-11) and want a day off from time to time. From what I've heard, HR employees will not address the situation and continuously refer employees back to management so I thought it was necessary to seek a second opinion. Thanks in advance.