The major problem is that TrueSky does its thing outside the way the rendering works inside the engine, while you can have translucent material able to cast a shadow, TrueSky is not a material applied into something, it resembles more a postprocess implemented into a plugin, so it has its own skylight, its cloud shape’s data is used to alter how the shadows affects the environment changing the colors onscreen, and since this work depends on the pixel depth, its major issues are exactly with translucent materials applied into the world, where it is difficult a common solution to know where each object’s position are in relation to each other, unless you classify one by one giving an order of priority which is supported by the engine. So, Simul knows this is an issue with TrueSky and they decided to implement their own ocean, so they can deal with such issues easily… and I will do the same, because this is the best way of doing it. Now the thing is, my Ocean will look better, and my cloud system will look better than theirs, but both will not have the same performance as theirs, but with the method I will use for my cloud/sky system, which is nothing related to theirs, it will still be usable for games and i can guarantee the clouds will work with any kind of translucent material on the scene.
With all that said, it might occur that this ocean does not work with TrueSky, I will even try, but it is not guaranteed it will. Btw I have just started the whole study on cloudscape systems like the one in Horizon: Zero Dawn, because TrueSky didn’t work with Community Free Ocean, back there two and half years ago… and still doesn’t work and won’t.