From what I've seen, at least in the USA, most any EVSE using 3-phase power, is designed for big things like commercial vehicles - busses, trucks, etc. While the J1772 protocol and plug supports it (as does the plug used in Europe, but few are actually supplied with it, if any), very few vehicles, and no cars that I'm aware of, have it.
A 3-phase power supply in the car would add a fair amount of cost for what seems like, not much benefit. Higher battery charging rate, more cooling needed, more weight for both the heavier components and the peripherals. I do not believe the cost/benefit ratio justifies it.
Better would be to have more CCS units around, which, at least since 2015 MY, all i3's have support for.
