I was able to solve this using the answer from @AlexTereshenkov to arrive at this workflow.

1. In the Project pane of ArcGIS Pro 1.3.1 I right-clicked on the enterprise database connection under Databases to open its Properties
2. I copied its Name e.g. N:\path\SDEfiles\TEST PROD [personal].sde (SDEfiles is simply a folder that I created to place *.sde files into)
3. Ran this test which printed Polygon and worked without error:

import arcpy
rock_unit_table = r"N:\path\SDEfiles\TEST PROD [personal].sde\Test.TEST.DETAILED_SURFACE_COMP"
print(arcpy.Describe(rock_unit_table).shapeType)
arcpy.MakeFeatureLayer_management(rock_unit_table, "rockUnit_lyr")

I was able to solve this using the answer from @AlexTereshenkov to arrive at this workflow.

1. In the Project pane of ArcGIS Pro 1.3.1 I right-clicked on the enterprise database connection under Databases to open its Properties
2. I copied its Name e.g. N:\path\SDEfiles\TEST PROD [personal].sde (SDEfiles is simply a folder that I created to place *.sde files into)
3. Ran this test which printed Polygon and worked without error:

import arcpy
rock_unit_table = r"N:\path\SDEfiles\TEST PROD [personal].sde\Test.TEST.DETAILED_SURFACE_COMP"
print(arcpy.Describe(rock_unit_table).shapeType)
arcpy.MakeFeatureLayer_management(rock_unit_table, "rockUnit_lyr")