I would say most RTS games are hard because they're in real time and you have to manage a lot of units and your production at the same time, and know the correct unit composition to counter your opponent. In AI War 1 or 2, you can pause the game whenever you want and continue to issue orders, your economy is a consequence of how many and which planets you have rather than how regularly you're managing your workers, and your unit composition is more about figuring out how to make a good army out of a randomized selection. One of the hard parts of AI war- deciding which planets to take- has no analogue in normal RTS games. When you fail at AI war, it's not because you didn't move your units in the right pattern, and it's not because you didn't notice a dot on the radar in time, it's because you made a bad decision about your expansion strategy or you underestimated the AI response to something you did or you don't understand how one of the mechanics works. Actually, it's probably that last one, at least for your first couple games.

So in short, skills from a normal RTS wouldn't hurt, but AI War tends to be hard in different ways.