In practice they do tend to be mixed, if not in exactly the way you describe. Immediate mode systems often retain/cache a lot of state under the hood for perfor

In practice they do tend to be mixed, if not in exactly the way you describe. Immediate mode systems often retain/cache a lot of state under the hood for performance reasons, and determine exactly what needs to be redrawn on each iteration. Virtual doms (React, Vue, etc) are a great example of this.