How exactly would any change in the PC controls break, or affect at all, the console controls?
They're totally seperate systems.
Three AMD platforms, yes. However, I suspect because it's the same hardware, the data structures would be common for all three with only one source code for the game.
For example:
At compile time you can pass compile time parameters to the compiller via macro directives such as "&compile=PC". This will generate the PC executable. A compile directive &compile=PS4 will generate the executable for the PS4.
However, the game source itself has many common data structures. Changing or adding KB control elements automatically changes the data structure for all three platforms, which may cause problems. BIO has no choice but to QA the changes on all three platforms to ensure you don't fix one and create another.
Which is why I am unsurprised at the length of time it takes to do fixes and PC UI improvements.
EDIT: Oh, and there is something called version control. Because team1 works on XB1 and team 2 works on PS4.. etc and because of common data structures you certainly want control and approve who is doing what and when.
In other words, you can't make simultaneous changes compile and test. If you do it this way, you have a nightmare on your hands. Elementary diagnostic procedures is the ability to control the test and be able to reproduce it. The "fix" must be tested on all platforms.... Look at recent Microsoft or McCafee... they shoved a fix out there and caused chaos...