No they aren't, because you forgot the little detail not every kind of PCIe card is supported, like those that folks using graphical workstations for CAD/CAM rendering, or those in VFX, might think of using.

Also not all kinds of high-speed network, or real time audio cards are supported.

Stuffing a Studio into a desktop case full of air, and limited set of supported PCIe cards, is a slap into the face of the hardcore users that still hope Apple cares about workstations.