A question is either on topic here or it isn't. That's determined by our scope, our mission statement. Whether the question is on topic on another SE site (even one that's not created) has nothing to do with a question belonging here.
As made evident in our scope, our definition of lifehack, and this related meta question, our scope is physical lifehacks. So long as the question meets our question requirements, it is on topic for this site and should not be migrated.
As for the particular question you brought up, it is about a lifehack related to spreading batter and meets our requirements, thus is on topic and should not be migrated. We'll have to continue to be careful with cooking type questions, but as Robert implied in his answer you linked, there can be some cooking related questions on topic for Lifehacks.
Cooking food is not a lifehack — not unless there's something so novel or so unique about the circumstances, that the solution isn't really well-known or already commonly taught in that subject space.
I'd say using syringes to spread the batter isn't well known nor commonly taught.