What's ironic is that Apple does all their mechanical CAD work for their products in Siemens NX running in Windows VMs.

I understand the need for it to be in Siemens NX, but do they really run it in Windows VMs? As far as I know NX isn't certified to run in VMs without Nvidia GPU passthrough (aka Macs). It seems more sensible to maintain a fleet of Windows desktops specifically for CAD and industrial control.

More sensible, yes... but less ideologically pure.

It could be VDIs, i.e. VMs running on another system, potentially x86 with GPU

This is insane. Is there no great first party CAD solution on Mac?

Tons of industrial software is Windows only, whether it's design, operations, or configuration & control apps for industrial hardware.

MacOS versions are more commonly found in the low end of the market, e.g. Fusion 360.

I guess not for this use case. There are many industrial use cases for which there are no macOS versions. In fact, Siemens NX was once available on macOS AFAIK, but isn't anymore.