It's almost certainly down to people using ad-blockers that are not working properly on YouTube, so they're just blocking the skip button but not the ad itself. As YouTube regularly tinker with their code to try and circumvent ad-blocking, this can definitely happen.
If you look at one of the photos provided by a Reddit user that's in the Android Authority article, for example, you can see this in the bottom-left corner: -
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YouTube does not allow unskippable ads longer than 15 seconds on mobile and 60 seconds on PC or TVs. There's no way they would allow ads that are an hour or more in length that are unskippable, cos nobody is sitting through one of those to watch a 10 minute video.