Um..Half-baked implies that it was taken out and served before it was ready. Completely baked is exactly what you want. The one sitting should say something like “You never even turned the oven on.”
I think in this case the point is in perfect timing. Arlo is already up, dressed, and enjoying possibly his second cup of coffee. He hears Janis arise and knowing what she needs first thing, times it to be ready as she walks through the door.
It’s the absurdity of having a garnish like a pickle served with dungeon food.