So, FWIW, that section (Time, LBB3 pp. 35-36) is not about keeping track of time in general. It's specific to a type of campaign where you have multiple groups, and trying to coordinate them. See also LBB1 at 5, explaining that a ratio of 20 players to each referee is recommended.
This error is similar to someone reading the LBBs today and assuming that everyone played OD&D using Chainmail for all combat (see. e.g., LBB3 at 31).
I can't even. That video is beyond stupid, first for trying to tell us that this guy discovered a rule no one knew about (um ... nope) and then telling us how games back then were played (yeah ... not so much).