Trains don't seem to respect the third stop in any of my systems, and will zip to the next ones to exhibit the same behavior.
While typing this, I saw the very same train from the video unload all 3 at the same stop, then continue to the next stations and skip the third drop-off on each, despite all of them having space, so it appears to be inconsistent.
This is my first train usage as of this save, so I'm unsure if it happens in other situations.