In practice, antialiasing is often a synonym for supersampling.Supersampling means that the image is rendered at a higher resolution and then a number of samples ( pixel reads ) are taken from the higher resolution image to actually draw the lower resolution image. The end result is the sort of pixel blending effect that you refer to. There are other ways to antialias, and I do believe that the Blitz3D broken implementation does do it a different way,.
And yes, in Blitz3D, it's broken.
And yes, in Blitz3D, it's broken.