Yup. Another prominent example is Amazon’s inability to sell books in the Kindle application on iOS, which has the same anticompetitive undertones given that Apple sells ebooks to users of its platform.
So not sure what you mean.
It’s the same (technically easier as I don’t need to convert ePub to mobi)
Apple owns a mall (iOS). In that mall, Apple owns a book store (iTunes). Amazon also has a book store in the mall (Kindle).
Apple does not want to sell Amazon's books (Kindle format ebooks) in it's store (iTunes). Ok.
Apple decrees that no store in the mall shall sell any books but iTunes books, which only they may sell. Not Ok.
In the brick-and-mortar world, malls are fungible, and stores that sell the same goods are fungible. The iPhone is not fungible.
Anyone that wants to constrain themselves to a single market, needs to accept the rules of focusing on a single market.