Not sure about DG but 3 phase power was the norm in IBM computer rooms so we never saw it as a burden. There was no neutral brought to computer panels either. It was all L/L load. They really did it to reduce the ampacity required (1.73 more bang for the amp at 3P). Back in the days when I was working in that field we had enough 3P motors to make 3p the norm. I agree single phase 208 power supplies were common but not all of them. The big switchers in water cool stuff were still 3p. There was also a large array of different type supplies. Some were real noisy. The 3705 communications controller used SCRs to pick off the DC directly from the 208 3P line voltage. That was a spiky sommich. By the 90s our mid range stuff was starting to be single phase but we still needed 3p for the old technology tape disk drives.
