Well. PS/Hyundai has put the warning for some reason. You genius guys were lucky not to have a hefty bill after blowing some critical sensors, but that doesn't mean you will always be lucky.
Let water enter the ECU somehow and burn it. The replacement ECU cost? Hmmm....
Seriously what's the fun in watching the engine being washed with high pressure water at the cost of potentially around Rs. 70,000 - 80,000???