LMAO, Moon the guy himself came into this thread, I'm honoured.
But yeah, I agree with the general sentiment. Fuck Google and fuck ads, but I cannot really understand how JavaScript being executed on your browser to determine if you are watching ads is legally problematic.
Regardless, in the case this is actually in breach of law, and YouTube gets slapped with a fine or something, they can always revert to the other method I mentioned of generating random IDs for ads, and refusing to serve your connection if you never loaded those ads with the unique ID tied to your session. That would work purely server-side and without any JavaScript.