Im assuming the guy didnt use detergent! Even just with water you have several problems:
1. High heat. Alot of these old components barely hanging on just the heat alone could ruin them
2. Breakage: running through high heat with water jets you can cause all kinds of problems with caps and resistors coming loose.
3. Toxicity for your food. Washing a corroded electronic board in a dishwasher can make your plates and cups toxic
so AGAIN PLEASE DONT WASH AMIGAS IN THE DISHWASHER,. and yes you may have further ruined the board by doing so luckily there is no shortage of a2000 mbs and they are cheap.
I've washed a lot of electronics in dishwashers over the years, including complete CRT monitors when they were really nasty and have had few issues although it's best to remove the flyback and/or focus divider if that is attempted. Electronics that have come from heavy smokers are nasty and going through the dishwasher removes most of the sticky disgusting nicotine/dust sludge that makes them really unpleasant to work on. When boards are manufactured they are washed in a similar process to clean off the soldering flux and other debris. That said, you have to know what you're doing, some parts like potentiometers and switches are not sealed and do not tolerate such aggressive washing well, and dishwashing detergent is quite alkaline and can cause corrosion if it becomes trapped so I use only a very small amount.
For high value vintage stuff like Amiga parts I recommend hand washing in a sink, use a small amount of liquid dish soap and a toothbrush or similar to gently scrub the nooks and crannies. If the water in your area has minerals in it I recommend rinsing with distilled water or isopropyl alcohol. After washing, allow it to dry thoroughly, I use compressed air to blow all the water out of spaces under chips where it likes to become trapped, then I set the board over a heat vent for several days to allow it to thoroughly dry before powering it up.
