Is there a technical reason that's not possible in a future update to NACS?
CCS2 has 7 wires. 5 for 3 phase power (3 phases + ground + neutral) and 2 more for DC.
It a pretty mad design. If you think about it CCS2 requires every single car to lug around a 3 phase battery AC-DC converter instead of just putting it with the chargers. Doesn't make sense.
3-phase -> DC is easier than single phase. One of the benefits of 3-phase is that power delivered is constant, so you don't need very big capacitors. That's part of the reason nobody makes a DC fast charger bigger than about 20kW.
Two wires is enough for 208V phase-to-phase from a three phase power source [0]. NACS supports three phase power sources in this configuration.
[0] https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2F...