When we used to assemble boards (we now contract it out) - we had two board washing systems.
First one for larger runs - industrial board washer. Looked like a mini-carwash that the boards went through.
Second one was a Sears Kenmore dishwasher. Used this for small runs.
Had a special soap for cleaning these plus it's own soft water source and waste water treatment.
Yes, there is no problem putting most electronics through a wash process.
Things that can NOT be washed this way:
Some trimmers that are "sealed" are not really sealed. They are often sealed from dust but not water.
DIP switches... NEVER. They will eventually develop a beautiful light blue-green patina inside and will stick in whatever position they were last set to.
Relays -- again, never.
Some voltage regulator modules (haven't seen any used on pinball machines).
Probably other items as well.
We never washed boards with IC's installed in sockets. I imagine when the IC is still installed, it might trap water in the bottom.
Don't do this with a dishwasher you expect to wash your dishes with afterwards.