To be frank I consider economy and government and social organization to be the same thing. To manage, to govern, to rule, to regulate. It's all politics, ie sometimes making rules or guidelines as a group, that are occasionally enforced through power.
Also "Governance" doesn't start with "Eco" and as such the word is not part of the name, which is what my comment was about. :P
But yes, it is indeed a separate word on a separate pillar/branch and I do like that your game's design goals are all about topics on things that are easy to break / hard to get right / cause a lot of conflict, etc. It's a good opportunity to collect experience and play around with something that would otherwise be difficult to experiment on.