> They argued that a peer-to-peer app based on "decentralized" crypto technology "would allow iPhone users to send payments to each other without any intermediary at all."
Kraken lets you access crypto that is held in custody by an exchange company. Ledger Live lets you access crypto that resides on a separate physical device.
To the best of my reading, plaintiffs argue that Apple is preventing people from holding cryptocurrency on their iPhone. As in, the private keys are stored in the app's secure storage space, so the crypto is actually "in" the phone and not with a company or on a separate device. So to answer your question, that's what it seems plaintiffs are alleging that Apple prevents people from doing.