Simply said, the power grid in central Europe consists of three parallel "power connections". Experts call this 3-phase, because every single "power line" is called a phase. (Technical department: direct current, alternating current, three-phase current). An 11 kW wallbox supplies a total of 11 kW, but these are distributed over the 3 phases. So basically it only delivers 3 times 3.7 kW.
Since the smart # family, without 22kW charger, can only charge with 1-phase 7,2kW, it is limited to a third of the wallbox output and therefore only charges 3.7 kW. To be able to charge the full 7.2 kW, you would need a 22 kW wall box. This provides 3x 7.2kW.