Minor quibble but, at least for music, most GC games used a native 4-bit ADPCM ("DSP", decoded by the DSP, or the ADP/DTK format, like CD-XA ADPCM and also handled in hardware), and the most common cross-console audio middleware (CRI) also generally used 4-bit ADX ADPCM. In this old list, everything marked ADP, ADX, DSP is using 4-bit (and others are usually just different containers for DSP): http://web.archive.org/web/20080420105759/https://hcs64.com/...
PS1 and PS2 were similar. I've usually only encountered 8-bit DPCM on PC, though the 3DO had a version in hardware.
The old table-driven style of ADPCM might be the poor quality the author has in mind, all of these consoles get much better quality at 4 bits, using the same kind of linear predictor (usually with 2 samples of history) with scales per frame as QOA.
Edit: I hadn't read carefully enough, QOA is doing something more complicated by updating the weights rather than using a fixed set of filters chosen per frame (ADX has only one per sample rate, GC DSP uses 8, XA/PS uses 4 or 5). That seems a little overcomplicated, but maybe needed at 3 bits per sample?