Just as well, because unless CiG code for it (and I've seen no evidence they have), the Procedural Generation in CryEngine isn't capable of generating those features. SC's procedural generation is barely worthy of the title, as it is in essence, a set of bounded Fibonacci sequences to give repeatable (and consistent in MP) randomness to objects and features i.e. the code generates a sequence from a seed to apply what looks like random orientations to a set of rock features, with some limits to prevent outlandish edge cases. What it doesn't do is work out that the rock features should be there and in that orientation due to a recognisable geological process.For SC where the number of planets planned with rivers is certainly less than 100 and already with hand placed elements, it's not really important.
This is one reason amongst many there is so much hand crafting in SC's environments....they lack to skills or leadership to develop the engine to do it vs. cranking out content that should come for 100th of the current cost.