Why would you need a warning about any kind of surgery video? Surgery by it's nature is usually visually "gross."
If the topic subject is "gross" (surgery, beheading, fiery fatality, etc.), I just don't click on the video.
I can see posting a warning if the video has unexpected graphic images that aren't evident from the topic title. Like, if the topic was "cute puppies" and the video shows puppies being tortured, I would expect a warning for that.
I thought "spoiler" meant a post where plot information from a book, movie, or TV show was given away. It "spoils" the surprise.
A "graphic warning" and a "spoiler alert" are not the same thing.