Didn't watch the video.
But agree with the others, the carbon ring is real - suppressed or not. The more over bore the cartridge, the more of an issue it becomes. Moderate chamberings, it has never been an issue for me. Never detected any carbon ring in my .221 Fireball, lol!
You can feel it, even when it's just starting, on a tight dry patch after a good cleaning. If there is a little catch, or feels like a slight tight spot right at the end of the throat, it could be the start of a carbon ring.
I deal with it similar to the others who have already posted. Good regular cleaning, then work some JB in the throat area is how I've always done it.
Most of what I shoot is pretty dange over bore. I like fast and flat and barrel life, meh... If you catch it and deal with it early, it never becomes an issue at all. So I check that tight dry patch every couple of cleanings and if I feel what might be even the start of carbon ring, I break out the JB.
- DAA