Some Status libraries suffer from README driven development.
That particular feature does exist and has a proof of concept but it was deemed too risky to add it at the moment given our time constraint, audit schedule and an Ethereum 2 launch just around the corner.
Note that we don't use the standard library async implementation but Chronos instead https://github.com/status-im/nim-chronos
The design of FastStreams requires a very thin "glue" layer between the library and the async loop back-end. Currently, the AsyncDispatch back-end is tested only through the AsyncPipe support defined here:
https://github.com/status-im/nim-faststreams/blob/master/faststreams/asynctools_adapters.nim
That's purely an accident from our own development needs. We use AsyncDispatch only in our chronicles-tail tool, but I consider the code quite stable and well tested (I use it on a daily basis).
If you take a look at the Chronos back-end, you'll see that the code is quite similar. Adding support for AsyncSocket and other types from the standard library should follow exactly the same patterns and it should go into the currently empty file sitting here:
https://github.com/status-im/nim-faststreams/blob/master/faststreams/std_adapters.nim