You'd expect more cores would be better, but most game engines were written a while ago and favored single core performance with a small number of threads. Starcraft II would be a classic example, it loves clockspeed. AotS is a newer game that responds well to more threads, but it took some time and a couple of patches to make full use of Ryzen's extra cores. Some older games are also receiving optimization patches, Total War did not run well on Ryzen but got a patch just last month that boosted performance by 10% or so. Newer RTS game engines will probably favor more cores but they're still trickling in.
TL : DR
It mostly depends on the game engine being used, older RTS games still favor single threaded performance, newer are shifted towards heavily multithreaded.