I’ve heard of it. Some old timers call it “steam cleaning”. I’m 58 and haven’t heard of it in many years.
I’ve also heard of people swearing by Marvel Mystery Oil. MMO has lots of information online.
Yamaha has a fuel additive called “Ring Free”
My way to de carbon is to remove the head and clean it up. You’d be amazed at what oven cleaner can remove from the head! Just wear gloves and eye protection.