I think there's a different term then moire. (not sure what it is called) We're not dealing with two overlapping patterns, just the dot display which creates the pattern. What the dot display was is up for questioning. A gridded pattern like:

or an alternating matrix like:

Take the image below and go into the post editor and grab a corner and scale the images and you'll see how possibly the larger waves of the holograms may have come about.

My guess is the filmed tv was on it's side, or the camera turned 90 degree. (this also seems to be the case of the shots in ESB which read horizontal) But much of this depends on the tv model recorded. The TV static when Leia's message resets could also tell us more. But if filmed in a certain way, like Harmy said at full 35mm resolution, they could read as our eyes see tv an image, with enough pixel bleeding to melt together, only when resized and contrast boosted does everything go haywire.