I've worked in some kitchens that are really good about this and actually follow through but the one I'm at right now is absolutely scummy about this. I got sent home early the other day because we were slow and one of the servers tracked me down on the way out the door to make me pay for a meal I ate several hours prior because I technically did not work a certain required number of hours in a given day to be allowed to eat. This is absolute bullshit on multiple levels.
Furthermore, if you are a line cook and your employer refuses to allow you a shift meal, I would encourage you to make yourself food without their knowledge and eat it on your own terms. You deserve moral permission to take food from your employer if they will not provide it to you. I have known plenty of people in restaurants over the years who do this and I applaud anyone who does the same.