I'm speculating here, but from my experience with Windows powered oscilloscopes: Windows is on the measurement device, it's not a networked or USB controlled peripheral with a documented network protocol connected to a standalone PC. When you open up "Device Manager" you'll see a bunch of specialized USB and PCI/PCIe peripherals that make up the actual measurement function and user-interface.

So the company selling the spectrum analyzer would have to publish quite a lot of their internal documentation regarding hardware registers for the data acquisition boards, and they'll be reluctant to do this: Much of a modern measurement equipment's functionality is inside the data processing, and by documenting the interfaces it would make it possible/easier to reverse-engineer or extent (without paying for options) the functionality.

> I'd think that for $300K you could have demanded an API. Perhaps on the next one?

"Why certainly, sir! We can provide that for only $EQUIPMENT_COST * 10. Do you prefer floppies or a CDROM?"

I wish I was joking.

Or terms that said the operating system should keep pace with update availability.