Some of the videos are merely travel log type videos, or family videos, but some are deliberately made videos which may have several scenes, and/or several takes to get it right.
Videographers making commercial videos use “sync-slates” such the Denecke TS-C Compact Time Code Slate - Color Clapper, which costs $1,180, to track their takes of scenes which they will eventually put together to make their video. That cost is certainly out of the realm of possibility for amateur or even pro travel photographers, seeking to capture video while traveling, document their travel work, or possibly create some instructional videos.