The recommendation algorithm isn't necessarily identifying this as shock content or gore, all it's doing is identifying it as having the hallmarks of something

The recommendation algorithm isn't necessarily identifying this as shock content or gore, all it's doing is identifying it as having the hallmarks of something that a certain circle of people engage with, followed by it deciding that everyone engages with it and it should be the default. It's possible that internally it's tagging it as gore, it's also possible that it's simply categorising it as "fast moving video with an abundance of red".