You can stretch it, but would you risk five hundred billion dollars on the judge agreeing with that stretch?

I wouldn't.

You can stretch it all you want but while iPhones may have powerful CPUs that could qualify them as "computers" they're not general purpose computers, so while I could use them to write an email and book a train ticket, I can't do any school or office work on them and iPads mostly remain Netflix/youtube/redit browsing devices for the couch after the honeymoon period is over so can you really put them in the same category as "computers"?

My smart fridge also has a powerful ARM CPU and a touchscreen and a modern OS. Is it also a computer? Can I use it for productive work? Doe every wearable and IoT device qualify as a "computer"?

So sticking back to general purpose computers that are not locked in a vendor ecosystem and let you install and run whatever you want from whatever sources, Apple is less than 10%, so yeah, with ~80% marketshare Microsoft is basically a monopoly in that space.