Mmm, Rubio averaged 16ppg on 42fg% and 35.3% from 3 in 24 games after the All-Star break. So yeah, it's rare but players do have hot shooting streaks for a long stretch and then regress.
Contract years anyone?
Another example, Dion Waiters. He shoot 39.5% on 3s last year. Even fully healthy, I don't think that was sustainable
Ricky has very rarely had high scoring games in his career. Mirotic, when he's gotten consistent minutes, has had a ton.