Why not?

How do you imagine that a cloud computing platform designed around running Macs with macOS would work for testing an entirely different OS running on bare metal on hardware that doesn't have a BMC, and usefully catching and logging frequent kernel panics and failed boots?

It's a pretty hard problem to partially automate for setups with an engineer in the room. It doesn't sound at all feasible for an unattended data center setup that's designed to host Xcode for compiling apps under macOS.