I'm curious, is there any advantage to this over software emulation, besides "I did it because I could"? (which is of course cool in itself).

It doesn't matter how fast your emulator is, throughput-wise. Your operating system (and other stuff) sits between it and output and input devices. And usually adds multiple frames worth of latency. There's ways to improve this, certainly, but you won't get that experience "out of the box."

Now, it's also possible to accomplish this by running emulators "bare metal" or "close to the metal" like my friend Randy did with his BMC64 project: https://github.com/randyrossi/bmc64