Most yachts in this video have evidence of being home built craft.

The only standards set forth as "classes" are by the governing bodies with a set of rules while design and manufacturing standards are set by the makers of each individual yacht. There are variables throughout the industry.

Modifications to design and manufacture of yachts between model years will generally change the standards for that model or "class" of yacht. Things like, yes that's legal now or no that's no longer legal! Standards/Rules are good from a "class" point of view but not good for advancement of a class. As we all know, rules are very stifling and it usually takes everyone wanting to do it for there be any changes.

Home built or hand made yachts are the ones that generally set precedent in design and manufacturing processes, that's how stuff gets invented. That's why landyachts have become what they are today. It is also the reason why Seagull, Airtrack, Manta and others are all in business today.