You do not have to let schools know unless you want to. I did just to let them know that I submitted the academic update and that they should be recieving my updated transcript soon since it may take PTCAS a few weeks to verify before sending them out
I actually spoke to the admissions coordinator at Duke this weekend during my interview and she said you should email because PTCAS doesn't actual alert them that the AU is done.
I would go ahead adn let them know just in case. It shows you are interested in the program and are on top of your game!