I Quote someone from Sky At Night who says - "Technically they haven’t imaged the black hole as it is a singularity, what they’ve done is clearly image the event horizon just as material is super heated then falls in and disappears"
Well, I guess that depends on your definition. Simply put, a black hole is a region in space from which nothing can escape, not even light. The event horizon is the boundary between normal space and the black hole. Does that make it part of the black hole? It probably is. And I’d say the even horizon is an infinitesimally thin line but I may be, and probably am, wrong about that.
I think you're absolutely right. In this view it's not even an image of even horizon, but particles sliding on it.
There's quite nice explanation of the topic in this video.