I've done this to give myself something akin to Cliff's Notes, to review each chapter after I read it. I find it extremely useful, particularly for more difficult reads. Reading philosophy texts that were written a hundred years ago and haphazardly translated 75 years ago can be a challenge.
That said, I have not tried to build this directly into my ereader and I haven't used Boox's specific service. But the concept has clear and tested value.
I would be interested to see how it summarizes historical texts about these topics. I don't need facts (much less opinions) baked into the LLM. Facts should come from the user-provided source material alone. Anything else would severely hamper its usefulness.
It's as open as most Android brands. I don't use any of Boox's services or apps. I installed F-Droid and use open-source apps from there. I use Librera as my ebook reader, with Syncthing to sync my book library between my desktop, ereader, and phone. It's possible to set up the Play Store but I don't bother, personally.
It's not a 100% smooth experience but I'm very happy with the F-Droid compatibility. I absolutely refuse to get locked into a walled garden.