I don't want to diminish the accomplishment; that seems like a very cool dataset and probably one that was really fiddly to pull together; but, if you are talking single-neuron resolution; I am curious about whether you can still call an individual sample "the human brainstem" rather than "a human brainstem" and what comparative purposes you can use it for without running into trouble with cases where there are multiple ways for a brainstem to be adequately healthy, so long as certain requirements are met, so you'll need considerably more samples to draw useful inferences about exactly what the problem abnormality is.
Same sort of thing as when "sequencing the human genome" was a big project. Obviously a major exercise in gene sequencing and a basis for situating subsequent sequencing operations; but once you start talking detail there isn't 'the human genome'; literally everyone has one; and it turns out that different differences matter or don't at radically different levels.
Presumably the methods used to do it once will be helpful in doing it more often in the future; but I'll be curious what we discover about the balance of 'normalcy' vs. some relatively subtle and confusing combination of surprisingly variable ways to have a brainstem that seems to work just fine along with surprisingly subtle, no ghastly big lesions, ways to have one that ends up being totally dodgy.