Are Bitcoin wallet apps on iOS really decentralized?

The only p2p support offer on iOS that I know of is the MultipeerConnectivity framework. According to its documentation, it only seems to support nearby devices (ref: https://developer.apple.com/documentation/multipeerconnectivity).

Now, by "truly decentralized," I mean not using any backend at all.

Maybe there is something that may be missing. If wallet apps are truly decentralized, how do they do it?