Even in places where they have to use the actual ingredients, there’s a lot of tricks to making it look different in photos. That burger might only be partially cooked to reduce shrinkage, then the burger and bun are frozen so they hold shape for the photo. Vegetables carefully picked out and arranged, tomato/pickles blotted dry, and the sauce applied with an eye dropper to provide visual balance after the rest of the burger is stacked.

I will say from my experience, that tends to apply to advertising photography for large franchises. If we’re taking about food photography associated with a high profile event or restaurant where food is actually served, there’s minimal difference between the photo plate and what’s actually served. Sometimes the photo plate is just one picked out while producing the ones being served, sometimes it’s the first/last plate and a person takes a minute to pick out the best looking of ingredients from the same container that was used to serve the rest. Sometimes it’s just an extra minute arranging the plate nicely compared to the last 150 that were done quickly to keep up with service. Often the photographer then gets to eat the plate they’ve just photographed.