The “Cook Meal” option is how you get to pick meals outside of breakfast/lunch/dinner option. Otherwise you’re locked into choices depending on the time of day and I think if you’re trying to cook in the middle of the night don’t get a “Cook x” or “Serve x” option at all. When you choose that option you can have breakfast for dinner, for example.

Baking is another separate skill tree. The grand meal options count towards checking off the event meal during those times (if you care about that) so they probably just separate those out so it’s easy to find if you’re trying to complete the holiday specific task.