All of the
Apple Store refurbs of the Studio so far have a 512GB SSD.
Leading to the natural conclusion: The lesser-capacity SSD is not suitable for high-end consumers who are the Studio's target market.
And they are returning the 512GB model in much higher volumes.
I think if Apple had made the Studio's SSD replaceable, no one would be taking about a new 27" iMac and the company would have a clear hit on its hands.
Instead, it goes down as one of their
questionable design decisions.