Thanks for getting in touch. I believe the error message you are seeing relates to the --variable itself, I can’t find any of our commands that would accept that as a parameter, thus it would be treated as an Unrecognized command argument.
To help troubleshoot, could I get some more details on your build and deployment scenario? Where are you trying to get the variable value to?
Looks like it’s pushing the correct value through in my test setup. Noting that the value itself is surrounded by double quotes. In your original example you had single quotes, which will not work.