No that's on the parent's for allowing their kid to have access to an account that can make purchases and nothing more.But one of the reasons that Apple have limited in store purchase, is to protect individuals from the drip feeding of charges that occur. Many reports of children playing games, that the parents thought were free, due to not having to pay for the app, and then large bills coming in. Whilst that is not Apple's fault, or that of the developer, one of the simple edicts Apple have been trying to apple to it's 'products' is simplicity, and ease of use.
Considering the market is so small for Epic, why does it bother. It has a product, and if it wants to sell it through a certain shop, then play by the rules of that shop, or go elsewhere.
ALSO that happens all the time even in apples walled garden and isnt at all the reason for apple limted in store purchase