Ah, then let me explain it to you:

The reason why Google doesn't just take a 15-second ad with a 5-second unskippable section and turn it into a 15-second unskippable ad is because people will get frustrated with Google/YouTube and leave.

The current system causes people to stay, and blame themselves for not skipping the ad - "I'm just being lazy, it's only a few extra seconds."

That is the dark pattern.

I think the complaint here is not exactly about the fact that you can't skip some of the ads, but that by varying the UI a bunch, users don't reliably "catch" all the skippable ads, so they watch more of them or take longer to skip them than would be the case if it was always immediately obvious what you could and couldn't skip.