The cyst mentioned in the original article (and shown in the MRI image at the top) is a posterior fossa CSF cyst that most likely formed as the result of hydrocephalus. Basically, it's the same thing. This is an example of how confusing all of the terminology underlying autism is. In some patients, CSF cysts, hydrocephalus, Dandy-Walker Variant and "autism" may all be very much related or referring to the same thing.

And to your earlier point, that SpringerLink article shows that they've been draining such cysts with shunts since at least as early as 1985, even if they didn't necessarily know what leaving them in place might result in later in life.