Every ADC/DAC used in audio in existence has an anti-aliasing filter, though. The Xiph video even talks about band-limiting signals with the 21 kHz cutoff filte

Every ADC/DAC used in audio in existence has an anti-aliasing filter, though. The Xiph video even talks about band-limiting signals with the 21 kHz cutoff filter he shows as the example. It's not talked about, largely, because modern circuit designs already have great anti-aliasing filters that have quite sharp rejection curves.