@MichaelWilson8 - Hi there! Would you be able to test this again? There was an update to the items in this dropdown after the release of ArcGIS Online 10.3. In ArcGIS for Power BI, we inherit the changes that are made there, and this data should appear properly.
Also, if it's possible, could you share the dataset here with me so that I can test it on my machine if this is still an issue? Thank you!