As a french I have never heard of anyone considering a burger as a snack, like a bag of chips, and not as a meal.
Do you use a burger as a side to something else? Like you would eat it with a kebab instead of fries? Or is it the same for the kebab?
I don't think you can select a meal in a restaurant, then have a burger instead of fries/salad as "accompagnement". You will also not find a burger in the "starters" section on a menu.
I don't know how old you are but I'm talking about 20 years ago. There is now a menu category ("snackings") that handles grilled items but that wasn't there in the 90s and early 00s, and it was the encroachment of brands like McDonalds and Cinq Mecs that made brands like Big Fernand and le Camion qui Fume possible (not to mention expanding Quick's menu).
I don't think you can select a meal in a restaurant, then have a burger instead of fries/salad as "accompagnement". You will also not find a burger in the "starters" section on a menu.