I disagree on the premise that audio glitches can and do happen on non-realtime operating systems due to the lack of guaranteed scheduling. For this 3D printer,

I disagree on the premise that audio glitches can and do happen on non-realtime operating systems due to the lack of guaranteed scheduling. For this 3D printer, it doesn't really matter, but for a lot of other things, I would feel uncomfortable trusting a desktop PC soundcard, OS, and drivers to perform glitch-free audio I/O. I would much rather send self-clocking commands from a PC to a hardware device which takes care of the realtime task on its own.