It's not an unethical hack, it actually helps the YT algorithm understand what category is the video part of. This works especially well in this scenario because kalari is a very narrow niche.

Tags do not boost your SEO at all, they rather help your video appear in the Recommended Videos section on the right of a YT video.

When I tagged competitors I was simply telling YT that it can show the videos to people watching another video from one of KalariLab's competitors.

There are 3 main ways to get views on YT when your channel is small:

1. SEO; 2. Homepage recommendations; 3. Recommended videos on other video pages.

The tactic with tags works only for the 3rd category above.

I hope that settles this discussion once and for all.

Sidenote: I still don't understand why this post was flagged...