Actually, I've known about these for years and it's mostly hype.
People here "brain-cells" and think of human brains or whatever, the fact is, most mammalian brain cells are made of the same matter. Rat/Dog/Dolphin/Human makes little difference. Using human stem cells to mass produce brain matter is merely bio-engineering, it sounds promising and it's nothing like trying to give sentience to "AI."
Brain matter is just matter, no different than assembling a computer chip as far as I can tell, there is zero sentience with any such matter created from stem cells and never will be. People think our minds = brains = souls is a huge lie of materialistic modernity. Our minds are more than our brains, and our souls are more than our minds.
I'm hoping that the regrowth of brain matter can help Alzheimer patients. Efficient computing sounds pretty neat as well but given how difficult it is to create mini-brains, I'm very skeptical of anything coming of it.