I feel this could also be Apple collecting common replacements from their customers devices and applying the suggestions to updated dictionaries. They must collect that data from devices, I would have thought.
The most likely explanation to me is that Apple probably has a feature which automatically replaces expletives so that users don't accidentally send messages with offensive language that was not intended. It's probably a simple substitution which maps known expletives to suitable replacements. A disgruntled developer probably added this substitution and, for whatever reason, it didn't get caught until it hit production. I don't know if this is true, but it seems like a reasonable explanation to me.