There are other sprays that are made to do the same thing, I think there's something called Orange or what ever........ If you can keep from over spraying belts and electrics it would be better, same with the hose, but remember that if you're driving though a raining down pore it's going to do the same thing under the hood.....
I've been washing all my cars and MC's since 1965 and each/most have 100k miles on them without damage , I even started years back using high pressure washes(holding nozzle not close) using wash, then rinse........ now days I've gotten into spraying 1st with BB then rinse with water.
It says in the manual not to wet the engine compartment, but Mother nature does it all the time..... Think it has to do with manufacture liability.