Documentation wrong for run-operation?

The problem I’m having:

All forms of the run-operation command that I can find documentation and examples for states that the --args parameter takes a YAML string in the form '{"param_name": "value"}'

This always returns an error that the YAML string is not valid. Through trial and error, I managed to get it to run using the syntax --args "param_name: value".

Is the documentation just plain wrong, or did I miss something? The documentation says YAML string, but the examples look like JSON strings to me… the error message seems to agree!

Many thanks for clarification!
Simon