Though they may not look similar enough to be confused for each other on the street, fans are essentially saying that Julia Roberts and Sandra Bullock are sort of interchangeable in their roles.
The fact that they were each in an iteration of 'Oceans 8' film also confused fans (Sandra in 'Oceans 8' and Julia in 11 and subsequent films). Plus, echoes another fan, both of them did "many romantic comedy movies" in the '90s and early '00s.
Plus, so many commenters noted that they had Julia Roberts confused with various other actresses (like Kyra Sedgwick in 'The Closer'), which led the OP to joke, "What I'm hearing is Julia Roberts isn't real."
Though they may not look similar enough to be confused for each other on the street, fans are essentially saying that Julia Roberts and Sandra Bullock are sort of interchangeable in their roles.
But on the face of it, it doesn't seem like Julia Roberts and Sandra Bullock really look alike. At least, not as similar as could-be-sisters Victoria Justice and Nina Dobrev, or the strikingly similarly redheaded Jessica Chastain and Bryce Dallas Howard.