Yeah, I had the same question in this post. Apparently, only the default will work. However, having now used the connector, I have found that this is not true. I haven't figured out how to reliably change the workspace, but I have done it. Read the post I linked and scroll down to @yookwi_hwang comment. Perhaps we can get Yookwi to give us some clarification. Because right now, I just logged into Power BI Desktop and it's pointing to a workspace that is not my default. So I know it's possible.
Workaround: create another email that uses the workspace you want as default.