I have no actual knowledge here beyond the article itself:

“Why 48 volts? Settling on this level holds the electrical system under the 60-volt safety threshold of what is considered high voltage, where power cables must be orange and special connectors, costing 10 times as much, are required, said Mary Gustanski, chief technical officer of Delphi Technologies.”

I wonder if your 50VDC limit is driven by the same “typical peak voltages for common battery chemistry” margin of safety I’m speculating exists?