The t= versus start= trap explains a lot of "timestamped" links that quietly begin at zero, especially when someone pastes a watch link into an iframe src. Converting every input to integer seconds first is the cleanest way to stop that. For changelogs and docs I'd add one habit: store the video ID and the start and end seconds as data, and build the URL when the page renders. When a video gets replaced, you update one record instead of hunting through pages for old links. Your chapters point fits that too. If the same three sections keep getting linked from the docs, chapters make them findable for viewers who arrive on YouTube and never see your site.