With riding motorcycles through water like that you really have to be willing to accept a lot of potential damage, the same as flood damage, potentially totaling the bike. The video shows the common stuff being gone through on the motor, but you only have so long to act before oxidation starts. It's a common reason that folks will leave sunken snowmobiles in half frozen lakes for days or weeks, if you don't have time to tear it apart right away, you may as well leave it in the water until conditions and timing are better to pull it out and then get to it immediately. There are dozens of things you might not think of right away that can be damaged easily by water, anything behind a seal, wiring and anything electronic, steering bearings, really any bearings, water in fuel tank and lines, brakes, tension springs, etc. There's an unfortunate likelihood that the guy in the video will be dealing with other issues caused by the water in weeks or months from now.
As for the repair it 20x times or throw it away, that's the moped way of life if you're interest in examples. Almost any kitted moped is always a work-in-progress and because mopeds are so inexpensive and accessible, there are a lot of owners who are either still learning and do some very shoddy work on them, or put little effort, money, and time into them and end up with cheap junk parts that never work right (especially cheap carbs, shipped new with bad jets).
Similar to the Top Gear Toyota Hilux, Discovery channel also had a bit with Charley Boorman where they put the C90 through a lot of abuse. Not the greatest copy of it, but it's online: