A lot of the real, industrial strength solvents are very corrosive. The Zep blue for example. Keep that off skin in an undiluted form, unless you like feeling your flesh turning to soap.
So you have "Joe" (Who is a **** of a guy) douching the engine bay of a truck he thinks he knows something about, with a corrosive solvent, then kind of blasting it off with a pressure washer.
All he accomplishes is to force this corrosive mix into ever nook and cranny. You have to rinse the **** out of a lot of those solvents. And if he's in a hurry and inattentive, he's also blasting it past the edge/lip seals of every bearing or bushing in there.
So the "easy fix" is not to have someone hover over Joe to make sure he's not doing this, nor is it to spend time teaching Joe how to not do the above.
Nope. You stick a decal under the hood telling Joe, "Don't do this".
My two bits?
You don't use overly aggressive soap mixes unless you have to.
The steam cleaner is not a magic fix-all for regular light cleaning, and a pressure washer will put water in places that ten years of deep fording won't.
Rinse with the garden hose, and a nondirected stream thoroughly. Take the nozzle off if you have to.
You want a good basic mix for general engine cleaning? A good shot of dish soap, a few cups of mineral spirits, then top off a cheap one gallon insecticide sprayer with hot water. Shake well, pressurize and spray . Let it sit a bit (don't let it dry) then rinse thoroughly.
