They are real for some. I have Aphantasia but my wife has Hyperphantasia so we compare notes often. Each of us are at the edge of the spectrum.

I mean, yeah, I can sort of replay things that happen in my head (obviously it’s nowhere as vivid as real life but still imagining through things I saw), and then sometimes I do realise you saw something significant that I hadn’t realised when I do so. So if that’s what you mean by flashbacks, then yes?

Yes, unfortunately they are. I say unfortunately because they are often connected with trauma. When something goes very badly, those memories can go cycling around one's head. PTSD can do that too. Some people relive wars years after they happened. It's very real.