Fact is, DLP knows rules are more consumer-friendly in France than in other countries of operation. They sometimes claim that something is enforced by policy (such as electronic tickets which they make you believe are non-transferable) but they somehow manage to let guests do whatever they want, as long as they have no legal way to prevent them to do so.
Regarding sharing meals, this is a tricky case since it could be argued that each customer in a restaurant shall be a paying customer. If one is sharing a meal, the other one might not be paying anything.
However, if everyone is indeed paying for something (be it a drink or a desert), then the argument goes. I can see no legal grounds for DLP that would allow them to charge a meal for everyone at a table.
Unfortunately, given the time being spent by DLP to actually train the staff in restaurants (hint : no time is allocated to training), I wouldn't be surprised by a cast giving false recommendation or rules. If you're willing to argue, ask to speak to a duty manager, and explain you just want to sit by the rules, and for whatever reason splitting a meal is part of the experience you want (which, again, should be fine as long as you are a paying customer).
There's a saying in French stating that false rules are only real for people who believe they're true.