At a low-level, for an ordinary working person, to get money you go out to work in some form and you earn it. In the modern era you rarely get given cash, it gets put into a bank account and you spend it from there.
This exercise is very low level - earn 'pretend' money, it's put into a 'pretend' bank account, and you can spend it in a 'pretend' shop.
You could start arguing that the shop represents an unlawful monopoly situation as you can only spend the 'cash' there, and so there should be at least one more shop and the two should compete with each other using market forces as the primary decision driver but...wait....these are five to eight year olds! Keep it simple and interesting or they will disengage! When they're a bit older the school can start explaining the more complex realities but this is a very good way to start it all off. Spark the interest. It's not ignorant or misleading and it's hardly leftie, it's teaching them some basic capitalist stuff technically.