That is an orthogonal matter and maybe my imagination is limited. But when I think of realistic new flags I do not think of a union jack missing its right diagonal in the corner (e.g. if we decide to decompose the UJ primitive).

We could also complain that the crescent is a complex primitive. Why not define it with three parameters: two circle radii with a center offset?

Choosing the primitives is hard and requires domain knowledge/taste, and finding a simple enough implementation solving for key usecases (e.g. decent coverage of maps, meaningful bit encoding) and descoping (e.g. deciding on no emblems) is also hard.

But I am personally impressed with the primitives the author created and the scope simplifications done to achieve it.