Not exactly sure what this video proved as related to myths, but
The time cheat you are using would effect peds, as pedcycle files and timecycle files relate and peds do (de)spawn according to time
The peds and player have a proximity at which they will not despawn. They may also not despawn if the player has them in sight (like yachts in GTA Online, or vehicles)
The peds didn't disappear because you were way too close to them, and you constantly looked back. Like you said in the video, leaving the entire area and returning caused them to despawn because you had left the proximity.
Weather also effects ped spawning, how they spawn, behave, walk, talk and react (rain causes them to run, etc, it also effects who spawn (the naked mansion won't spawn in the rain, etc).)
Great video, I liked how it was structured, I also liked the interaction with your audience, rhetorical questions, referring to what you like, don't like, etc, about the area you're in. Good theme.
Yeah I noticed but not mine. Just a decent video I found while browsing myths on youtube that I thought should be added to the myth page because it goes into the cheats more while the other video does not. So two sides type of thing.