It's not reading what the person's brain is interpreting the image as, but rather what they're currently seeing. I wonder how different these signals are.
It's a pretty big difference since the only signal they're getting is what the eyes are currently seeing. Essentially they're using a $1million fMRI to poorly do the job that a $5 dollar camera could do.
This is still super cool, but not quite our wildest scifi dreams.
From what I understand, memory cells literally reproduce the original brain signal just as if it were coming from outside stimulus. Like playing the brain waves off a tape recorder.
I can't recall pictures of events that happened yesterday with anything resembling what it was like to be there and experience seeing the events in person. I can construct images of what things might've looked like, but the creative process of recalling that memory feels awfully different than experiencing events in real time.
There is certainly some evidence for "replay", but it's generally thought to be involved in "writing" it into longer-term storage rather than the storage mechanism per se.
OTOH, there are some cool results with Hopfield-like networks where applying part of a pattern (somehow) cues the brain (or network) to produce the rest of it.