Force Secondary Axis Not Possible?

Hello,

I'm working in PowerBI in the hopes of replacing tableau.  We often use dual-axis charts to show $ and % side by side.  I think I've found an issue with Power BI.  If possible, I'd like to know if I can get confirmation or if I'm not doing something correctly.

I started with this tutorial: https://powerbi.microsoft.com/en-us/documentation/powerbi-service-tutorial-customize-x-axis-and-y-axis-properties/

In my scenario, I have "Wait Time" and "Abandon Rate".  The wait time is typically less than 5 minutes for a phone call.  The Abandon Rate is a % (a number less than 1).

Expected Behavior:  I expect that if I'm using a "line and stacked" column chart, that I will always be given a secondary axis for the line chart as long as I turn the secondary axis.

Actual Behavior:  It appears that PowerBI tries to outsmart me.  It looks like PowerBI won't even present me this option unless my two values are a factor (unknown) different than each other.  I can verify this by toggling my wait time between average and sum wait time.

- When I use average, PowerBI forces me to use the same axis even with line and stacked column chart.

- When I sum, the numbers are so far apart, that powerbi decides to let me use a secondary axis (I actually can't find the secondary axis toggle, but it works as I would expect with a secondary axis).

How can I force PowerBI to give me a secondary axis?  I'd appreciate anyone's feedback.

Thank you,

Dan