There are kernels running in almost every piece of peripheral hardware you own. If you have a modern WiFi chipset, LTE baseband, or GPU it's certainly running a

There are kernels running in almost every piece of peripheral hardware you own. If you have a modern WiFi chipset, LTE baseband, or GPU it's certainly running an RTOS kernel. Once you switch to a packet-based protocol with multiple concurrent tasks (decode, packet receive, link negotiation, etc.), it just makes sense - either you're implementing timeslicing / scheduling on your own or you can let someone else do it. The issue that causes poor video quality isn't that Apple chose to run XNU or use an SoC for their adapter, it's that they chose to use H.264 at a low bitrate due to hardware support constraints rather than another encoding scheme which could offer less lossy video.