The kid did a great job. It's old school vs new school.
Water was an old trick that would blow engines because the steam made way too much pressure for the engine to handle if done wrong. It was a trick of last resort. The kid knew enough, and even mentioned it a few times to warn people with his Seafoam.
With fuel injection you will not get the carbon build up like in the old days. What he viewed as a carbon problem old school would view as fairly clean. Letting the Seafoam sit on the piston head was sure proof the stuff works using his camera technique.
Kudo's to the kid, all he needs is some mentoring, but he's doing a fine fine job. Been using Seafoam for over 40 years, it does what it says.