It’s a stretch to equate Apple PayCash with cryptocurrency. PayCash is equivalent to PayPal, Venmo, and Chase QuickPay. It’s a way to store and transfer value in a standard fiat currency and the balance in the account is valued based on that standard currency rather than something new. The exchange of funds from person to person is more like using AirDrop for cash rather than anything blockchain-like. The functionality is centralized with Apple rather than a regular bank, similar to PayPal.
Now, sure Apple could decide to create a new cryptocurrency to hold that value in PayCash. But I struggle to see why they would want to.