It is one thing to no longer offer functionality, but it is quite different to remove functionality with a firmware update.
I suspect Shimano said they were no longer going to allow Hammerhead (now part of SRAM) to allow the Di2 display and control functionality in their new devices, in order to undercut SRAM's sales. Hammerhead/SRAM probably responded by saying "ok, if that is how youy want to play, we will delete it in our next firmware update for current users", which will screw Shimano and make them look like the bad guys.
This is yet another example of how the customer always wins with a Free Market(™).