I'd never known that lots in general had a 20-sim limit. (
@Playalot Thanks for that gem!)
"Recommend dish" is a tricky social. If a sim is recommending when a waiter comes to take an order, no waiter will ever return to that table to take orders. At least, that was my experience.
For that reason, I stopped using "Recommend dish."
Just now, I fired up my former Restaurant Wars file and opened the restaurant for business from my home lot.
When arriving at the restaurant 30 minutes later, I count exactly 20 sims at the restaurant: my owner sim + 5 restaurant employees (host, 2 cooks, 2 waiters) + 14 diners at 8 tables
Of course, this still doesn't prove conclusively whether the 20-count must include the employees or not, but I'm too lazy to keep testing.
@coolsim9999999 I'll be interested to hear what you find!