I’ve built bathrooms, and then come back years later to have to repair tub surrounds. The aqua board, or whatever they call it has a mildew-cide, and different colour paper, not much more to say for it than that. When it gets wet, it will be a tear out anyways. It also wicks moisture just great, so I will never use it again. At least a strip of cement tile board with a slight gap to arrest wicking should be used at tub level. If using a glue in surround, plywood or PT plywood could be used above that.