I had a play with the Developer Workspace a few months ago. After an interaction with developer support I had the light bulb moment.
The Developer Workspace is really just intended as a convenient way for developers to assemble information about their projects and push it into ‘the API’ (for want of a better term).
It is doing the same thing that could alternatively be done using the CLI or calling the REST API directly.
You shouldn’t expect an app created using the CLI to magically appear in the DevWS, anymore than you’d expect an app created in the DevWS to magically appear as config files in a folder where you use the CLI.
It might be reasonable to expect the DevWS to be able to import information from the API in future, and reverse assemble a project, just as you can manually import information from the API using the CLI and work with that.
It may be that the DevWS can currently do something the documented API doesn’t. However that would be something not yet available from the CLI and REST API eather than anything fundamental to the DevWS.