They were originally from the Outdoor Grill appliance (the one with a grill grate and blue bowl-looking base). They will likely return to this appliance once you finish the side goal, or the goal timer expires (whichever comes first).
On a personal note, I wouldn't mind if they stayed on the basic Grill appliance. The Outdoor Grill seems to have become a mainstay for the 5-day goals, so it consistently has new recipes added. Plus, this recipe seems like an actually sensible recipe for a basic Grill to have (still confused about the Tres Leches lol). But that's just my two cents