Seeing this build of MK1 for the Genesis (from CES 1993) is a strong reminder of just how willing publishers were to put early builds out at tradeshows. It certainly ain't like this anymore.
I thiiiiiink the difference is that back then, trade shows were... well, trade shows, not open to the general public. Anyone there had some level of industry knowledge and knew what unfinished games are like. Eventually trade shows were opened to the general public, and that's when companies had to hide how the sausage is made, because the general public doesn't know how to interpret what they see. I mean, people saw the GTA 6 leaked vid and thought the debug UI was actual game UI. They complained it was "too much like Watch Dogs." Can you imagine