Arent YouTubers always complaining about YouTube, which is their source of income?
While making money out of it.

Youtubers are making this more than what it actually is. Sure it will hurt some like kid content because people can't be parents and do their jobs themselves, but for the majority of users they can set their channels to non kid content and move on with life.

In this case, yes some of them also complain about Youtube and the way Google/Youtube shoved the accusations and fines over to the content holders. But overall it's about interpretation from FTC of outdated Law that was vague to start with.

Yes it's partially about advertisement income for the complaining youtubers. This interpretation would also apply to the advertisers after the FTC is done with Google, Youtube and their subscribers. No telling who's next, could be Steam, or:
Imagine "everything with animation" being seen as "targetting kids". With the precedent created at Youtube, that would aso apply to xrated Final Fantasy parodies at Xhamster and Pornhub, or Shadbase and DevianArt at their own websites and at Steam. What about all them nude mods gamers like to make and use for Skyrim, Sims, GTA and so many other games?

My assumption would be that YouTube is a business, and in the business to make money.
Plenty of YouTubers are making money outside of YouTube, the ad revenue market is over saturated as it is, Patreon and sponsors exist and provide creators much more freedom anyway.

When is YouTube precedent applying to Pornhub in the past?

When? If? We'll see in the near future, or not. If an interpretation of the Law is applied to one and accepted, that interpretation would apply to all.

The law is the law, YouTube is not the law, so YouTube is not really relevant at all.
And they have a different business model then PornHub, a different audience, etc etc.

It looks to me like YouTuber speculation. Just look at the 5 videos above, the preview of the last 3 is all pedding merch, obviously really concerned about the laws.

Send me money now, because something really dangerous will happen.... or it wont?

No, "the Law" is not "The Law". It's about the interpretation and that may vary in different times and/or circumstances. Interpretation would usually be made by Judges. Sometimes agencies may also create interpretations. In this case, it's the interpretation of the FTC that's worrysome.