/v1/shell/view api can't return output incrementally when running command using shell/exec

I tried to run a command using async mode by calling /v1/shell/exec api, the command will have stdout output.

At the same time, I use the session id returned by /v1/shell/exec api and call /v1/shell/view, I expect to see stdout for the command I ran, but got empty result in 'output' field.

Only when the process finished then I can get the stdout for the command I ran using /v1/shell/view.