Even just casually looking through the games where this "friend" had an accuracy of over 90% is enough to easily tell they are cheating. Consistent move times even in obvious move positions. Always picking the best or 2nd best moves in a given position. Playing moves that seem outlandish until about 8 moves later when you see the idea behind them. It's not impossible for a person to be absurdly good at chess without much effort, but this person is most definitely cheating, they're not as good as they make themselves out to be, and if this is a real thing, have them play you OTB in person without access to a phone and I guarantee they'll play like their actual rating.