[mosheroperandi]

I think it's the case as depicted in the first radar image, UAL1 turned 90-ish of degrees right on the exit from the taxi-way, and the other three lined up. It could be the angle of the camera is such that it's an illusion they're all in a straight line. That probably still gives them plenty enough view out the side of cockpit to see that the plane they're expecting is heading behind them and not in front of them where it should be.

I think the orientations in the subsequent screens where UAL-1 looks turned around are probably a case of the radar over-extrapolating from its heading from the turn and then not being able to tell its heading while it's parked.