Every new OSS repo's README should convince me to try it instead of the current standard tools, or at least compare it to them. In my case, I'd want to know what makes it better than Vuex.
It does have the key points listed in the readme. It probably is so obvious. Let me summarize them here.
1. Simplicity - The concepts of XSM are straightforward and easy to grasp. Whereas, the concepts of Vuex are not as easy to understand.
2. Vuex is for Vue only. On the other hand, XSM works Angular, React, and Vue. Learn once and be good with the 3 frameworks. Chance of code reuse with XSM.