Cool. Let's see the methods paper they used to produce this model, then let's see the independent validation papers which would show us that the model is accurate in compared to previously established information. Then let's see an independently authored paper on a unique speculative use of this model that has positive results.

This model is in its infancy. It still needs a lot of experimental work (5 years? 10 years?) and in general the more complex models take a longer amount of time to be validated and widely trusted. A great example is the humanized mouse model, which is super complex (though not as complex as a brain) and took somewhere between 3 and 10 years depending on who you ask to go from the point of the OP model to mainstream accepted usage for some purposes. Maybe 5 years down the line we'll see something come out of the new brain model.

Brain science isn't my expertise, but there's a couple of other tidbits that caught my attention about this model. First, its vascular structure is missing entirely. I'm guessing the level of oxygenation of the fetal brain is important, but there may be ways of controlling for this gap. Second, gene expression isn't 100% equivalent to an actual human fetal brain at this level of development. There are probably ways to control for this also, but it's still a flaw. We don't expect models to be 100% true to reality (after all, it's a model), so I expect that these holes aren't going to prevent this model from being successful and useful.