Not a specialist here, but my understanding is that whether a service is or not anticompetitive is subject to how its market is structured. So e.g. if you're no

Not a specialist here, but my understanding is that whether a service is or not anticompetitive is subject to how its market is structured. So e.g. if you're not a dominant market player then it "is" not anticompetitive ("is" in a pragmatic way, i.e. you will not be prosecuted), whereas if you are disrupting the market it is. All that to say that currently the market for voice assistants is nascent. No one has paid (directly) for Siri or Ok-google, and amazon can also make the case that you don't pay for Alexa, you pay for the device. Now that OpenAI has a better service, that is also unbundled from hardware, and understandably people might want to substitute Siri, then iOS only offering Siri can start to be considered anticompetitive.