I wrote something like this a long time ago. The customer's request was: "don't make this software produce swear words on its own". Note: on its own.
Producing "trump is …" when a user wants that is one thing. Producing that when the user wants something else could be construed as coming from the software itself, and we all know that people looking for a shitstorm will seize the opportunity.
So probabilistic software like a swipe interpreter will often be written to avoid some guesses, to lessen the chance of a shitstorm. Users who want that output have to use a dependable input method instead of one based on probabilities and guesswork.
IMO this avoidance isn't among the ten worst consequences of shitstorms.
An even more generous interpretation (not saying this is the case and a complete excuse, but might explain some of the choices) is that there are some phrases people do not want to type by accident.
“Male chauvinist pig” is something many would be very upset to send to their boss by accident. So it’s perhaps understandable some such phrases are not excluded from the guesswork.
Isnt the regular keyboard on iOS typing also probabilistic? I thought the entire claim to fame of the original iPhone keyboard was how it could determine which key you meant based on letter frequency / word usage / etc. Does that mean it can also stop you from typing certain things? So whats the difference between the swipe interpreter and the fat finger interpreter?
As another example, imagine if "trans women are" autosuggested "men" or "ugly" for the next prediction.
This would probably be a bad customer experience for many people, even if Apple could prove these are simply the most common n-gram completions.
And if they altered their training data to avoid completions that are politically unpalatable, IMO that's actually much much worse than a grey list.
I'm a big free speech guy but this one is genuinely a bit complex.