Async RecordSource methods mentioned in docs but don't seem to exist

[FezVrasta]

Hi, the documentation here mentions:

RecordSource (type): A collection of records keyed by their data ID, used both to represent the cache and updates to it. For example the store's record cache is a RecordSource and the results of queries/mutations/subscriptions are normalized into RecordSources that are published to a store. Sources also define methods for asynchronously loading records in order to (eventually) support offline use-cases. Currently the only implementation of this interface is RelayInMemoryRecordSource; future implementations may add support for loading records from disk.

But the RecordSource interface doesn't define async methods, nor any of the child interfaces.

Could someone please help me understand if the documentation is outdated/wrong, or if I'm missing something?