I see what happened. They changed the standard configuration, and it now requires a ground lug. It would be best to change the cable to ground the appliance. They explain it in that link I posted just above....
Yes, the range draws a heckuvalot more current, and the differences are a lot more than just the plug, the home run has to be a much larger gauge wire than for the dryer run. Both are 220V, so be careful out there. I lived in a house that had a three phase service, that led to strange things in the wiring.
Three-phase gets really weird when you talk about solar cell interfaces. Best to avoid them.
But even two-phase can be problematic. If you lose one phase of supplied power, the other phase can burn out motors which don't have circuit interruption. The way to protect the motor is to route its power through a contactor whose activation coils depend on each phase in turn. If any phase drops out, the contactor opens, protecting the motor.
The Uncle-in-Law knows what he is doing apparently, this dryer plug thing didn’t phase (heh) him at all. He had no problem changing it for the 4 prong.
Now for the water heater.