More accurate to say that fortnite is developed alongside unreal engine, they make unreal engine in house so they make their own engine. For example unreal engi

More accurate to say that fortnite is developed alongside unreal engine, they make unreal engine in house so they make their own engine. For example unreal engine 5.0 was very buggy, since they made it to work with fortnite first so only fixed the features that game used.