I'd argue that there is a substantial difference - if the staff of a film production (or any business, really) are already working on-site together, then them a

I'd argue that there is a substantial difference - if the staff of a film production (or any business, really) are already working on-site together, then them also eating lunch together does not create additional "connections" like a dining place that's open to the general public does. The policy goal is to minimize the number of people you meet. You meet your household, if you have to work non-remotely, then you meet some coworkers (preferably a limited amount and always the same, separating a company in teams/"bubbles") and ideally that's it - it makes all sense that places where you'd be eating together with random strangers should be restricted much more than work lunches where outsiders are excluded.