It is overkill. Easily could have been done with a 400/320 class service, including two 11.4 kW EVSE circuits. I have done a load study that proves that.
I have proved that empirically too. The meter is a Class 480 , which feeds three 200 amp main disconnects (which are built in to the three Generac transfer switches), and those feed the three panels in the garage. Not counting the EVSE circuits and pool heater which we rarely use, with almost everything on (all lights, a/c, ovens, electronics, pool pump (we have gas hot water and cook top)) the load is less than 150 amps. Both EVs charging at the same time would run that up to 220 amps.
But I am glad to have more than I need. Made installing the EVSEs very easy.