Yes, I've seen that convention, which further adds to the confusion. But there is a sub-package named arcpy.md (not just an alias), and my understanding is that it's pretty new.
(arcgispro-py3) C:\Program Files\ArcGIS\Pro\bin\Python\envs\arcgispro-py3>python
Python 3.6.9 |Anaconda, Inc.| (default, Jul 30 2019, 14:00:49) [MSC v.1915 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import arcpy.md
>>> arcpy.md
<module 'arcpy.md' from 'C:\\Program Files\\ArcGIS\\Pro\\Resources\\ArcPy\\arcpy\\md.py'>