Understanding guideline 1.2: Referenced definition not expanded

The understanding page for guideline 1.2 teases a glossary definition for synchronized media that isn’t there. 

https://www.w3.org/WAI/WCAG22/Understanding/time-based-media.html

Yada yada yada:

https://github.com/w3c/wcag/blob/43b7ca382ed41b6ab4b370185ef4132642fb4d91/understanding/20/time-based-media.html#L58