I don't think so. It's more akin to not posting a sign saying "our landlord charges us $5,000/month in rent" in a brick-and-mortar shop.
At the end of the day there are costs associated with doing business online. If Facebook was able to have their own payment processing pipeline, and still charged no cut, that's them processing payments at a loss, and subsidizing it with other income streams.
The Apple cut doesn't just cover payment processing though, (in Apple's opinion at least) it also covers the costs of maintaining the app store, reviewing apps, developer tooling etc.
There's really two separate questions here, is 30% as a cut for the entire App Store ecosystem reasonable, and is it reasonable to charge a cut paying for the entire ecosystem to someone who really is only "getting" the payment processing parts of it.
In a sense, when Facebook is providing this kind of platform, they're essentially competing with the App Store. Instead of whomever is running "Jasper's Cooking Class" making a cooking class streaming app and posting it to the App Store platform, they're able to use the Facebook platform to provide the same service. Because this becomes sort of a platform-in-a-platform, it starts getting expensive pretty quickly, because you have to pay for both.
Of course, the people behind "Jasper's Cooking Class" (presumably Jasper himself) are probably not in a position to make an app and posting it to the App Store, so Facebook providing a lower barrier to entry is probably a good thing for the market as a whole, but they're not doing it out of the good of their hearts, it's still a very deliberate business decision, aimed at keeping people on Facebook, where the users are monetized in other ways.