See the title picture! “Theoretical calculations predict an event horizon to all black holes, obscuring the central region in accordance with General Relativity. This is a prediction that has never been tested observationally.”
What we see on that picture, generated by calculations, is the effect of the black hole on the light that shines from behind of it, and that is much bigger than the size of the black hole itself.
The expectation is to really make a photo, instead of just “it should look approximately like this.”
See also the last picture in the text: “Simulations of how the black hole at the center of the Milky Way may appear to the Event Horizon Telescope, depending on its orientation relative to us.“