Otherwise, I'm really not sure what that "it's not Redux" comment means, either.
edit: Oh, crap, I just made a software/car analogy. I hate those.
Vanilla Redux on its own is like Linux without an userland, so you have to implement yourself.
Redux Toolkit is a proper Linux with GNU userland. It's ready to use, and people can even use each other's computers without reading through the source code!
It doesn't make a lot of difference for smaller projects, but the thing about Redux is that as soon as you have 20+ or 30+ people working on the same codebase you get a hodgepodge of different patterns and structures. Toolkit solves it.