I think this pattern is a good fit for simple cases where the actions and reducers are mostly boiler plate. If we have components that have very complicated reducers/actions, perhaps it would make sense to keep them separate (or consider refactoring the component into smaller, simpler components or to move some of the logic out of the store).
From a reviewer stand point, it is much easier to read and understand a 100 line file than jumping back and forth between two 50 line files. And from the examples at least it would seem this pattern would potentially also reduce the size of the files as much of the boilerplate is eliminated.
Perhaps it would be a good exercise to open a quick POC PR that adds the redux-toolkit library and take one simple component to change to using slice to demonstrate what it would look like and how much simpler it would be?