The simpler implementation might indicate that the rax developers are trimming overcomplicated bloat, or culling features that don't align with specific needs of Alibaba. Or maybe they're just removing code they don't yet understand the necessity for. It's not immediately clear what tradeoffs each are making, but having rax audit what's really necessary could be a good thing for everyone.
Looks like the Rax version is based on React-Redux 4.x, which was was primarily a single file and kept most of the logic in a React component. React-Redux v5 is a complete internal rewrite that pushes the logic out into memoized selector functions.
In fact, it appears to be 98%-ish the same as React-Redux v4.4.6. They've added semicolons, swapped out the React imports for Rax imports, and shuffled the order of some of the methods, but the code is effectively identical.
react-redux is definitely super bloated right now. It's packed full with method overloads (that are super confusing if you read their definitions in the doc as opposed to looking at examples), and performance optimizations that involve looking at the function arguments, memorization, etc.
It's cool and needed to cover all of the cases and edge cases, but it's easy to see how, if you don't need that stuff, it can be reimplemented in a fraction of the code.
In fact, it appears to be 98%-ish the same as React-Redux v4.4.6. They've added semicolons, swapped out the React imports for Rax imports, and shuffled the order of some of the methods, but the code is effectively identical.