I'm retired out of high tech. I worked with one person who could legitimately multitask. I have memories of him simultaneously debugging one program, writing an unrelated one (different monitors, debugging in assembler, writing in C), having tech conversations going with one coworker on the phone and another plus me in his office (talking, I think, about datacomms w me & a chess problem w the other) all at the same time. He and Dan Bricklin came up with interactive spreadsheets on PCs.
So yeah, they're out there...