It may not matter who did it, it is history. The question is whether you want to have it re-done properly by you or someone else?
On the boat in question, the wiring would be the least of my problems. I started the thread because I had doubts about the credibility of the seller and his claim about where he had the motor installed (and several other issues). Ironically, I suspect the seller would be the PITA customer Jgbrown
describes. So, maybe the installation was done at the reputable shop and they cobbled the wiring together to get rid of him. Unfortunately, that comes back on them, as I now have doubts about a shop I previously held in high regard!