It is fairly normal for firmware to be updated overtime. Whilst I don't know about your specific update my car received several control unit software updates back in May 2017 as follows:
Engine Control Unit Software - Motor electronics MED 177AMG for combustion engine M152
Electric Parking Brake Control Unit Software.
Electronic Stability Program Control Unit Software
Fuel Pump Control Unit Software
I make a point that every time the car goes into the Dealer Workshop I ask them to check that all of the control units software is up to date.
I am sure that my car had already received some software updates in the 5 years prior to my ownership.