I can confirm that our induction stove is very fast, much faster at boiling water than the (domestic) gas stoves I've had experience with. A pot of water really does boil in under two minutes, so I wanted to question your math, but it seems correct :-). The problem here is the quantity, why are you (gp) boiling 7 liters of water?

edit: the boost is more powerful (3.7kW for the largest zone), but still. That's time limited (10 minutes or less), and limits the current to the other zone on the same phase.