It was a bug and they fixed today : Fixed an issue where autonomous actions would automatically turn off when family members moved to eat after a meal was prepared
Also, it’s not as awesome as you said. Since they serve meals every five minutes, my teen’s homework ended up disappearing because the stepmom wanted to serve the table. I’ve seen a lot of people on Discord mention the same issue as well.
Oh ok, I didn’t experience it that much at all and I only gave feedback based on my own gameplay. In that case I’m glad they fixed it then 
This is happening to me, too. My zois either set the table with magical free soup, or they cook and set the table for 4. I have 2 zois, mother and teen daughter. The daughter was doing her homework and the mother cooked family egg toast and set the table. It caused the homework to disappear. I can’t find it anywhere, it didn’t go back to the daughter’s inventory. It didn’t clip into the table, it didn’t go to the bookshelf. It’s just gone. Homework is already very buggy so this is disappointing.
This issue happened to me as well before crashing. The Zoi sets the table with the soup and regardless of the task they are doing, everyone will join to eat this soup and search for a bin or sink to clear it up afterwards.
The most frustrating part is that when this was being served I had already selected a family meal to be cooked and when the soup was set, the pan remained on the stove while the zoi all gather to the table. When they’re done cleaning their bowls, the pan just disappeared and I couldn’t continue cooking the meal. This must be something to do with the cafeteria settings in the school.