I am using Pro 1.1.1.
I have an esri basemap and one layer of my own. The spatial reference of my map is web mercator.

I then use the Create Map Tile Package tool to create a .tpk. It appears to complete successfully, and i can upload this .tpk to AGOL for sharing with my apps, but my app is expecting the spatial reference to be equal to WGS_1984_Web_Mercator_Auxiliary_Sphere but instead it is None and therefor doesn't not work in my app.
To check all this I opened the .tpk in notepad for viewing, and i see this:

Instead i would expect to see
<spatialreference>WGS_1984_Web_mercator_Auxiliary_Sphere</spatialreference>
How do i ensure my .tpk has the spatial reference correctly defined?