What else could it mean? Aren't "views" something that matches with "watch"? Maybe I'm missing something from how YouTube works, not a big user, happy to be corrected :)

It could mean that it marks the video as watched but without increasing the view counter. There are multiple signals that youtube had as a view counter or measuring what parts of a video were watched. Just because youtube knows a video was watched it may not increase the view counter to avoid bots or just because.