Most important lesson: This model has a newer and very different chassis, the underside has a monolithic polyethylene base that is very difficult to remove. The diverter motor is accessible but just barely with an offset wrench. Also, the sprayers are quite different from the video, I could not figure out how to remove them. Note that the LG calls the diverter a Vario motor.
I replaced the motor but this did not fix the issue, so I called in the pros. They confirmed that the motor was not the issue, but discovered two round metal punch-outs that were holding the internal plastic valve immobile. Removed the obstruction and the problem solved. This dishwasher includes an elaborate filter system that makes it all but impossible for objects that size to have been washed into the system, so going to file a claim with LG.