That's the darn-est looking thing I've ever seen?
You are in a situation.Since he is going to be there a while I would give him an (as in one)opportunity to make it right.
I would get the plans and discuss the plans with what you see.When
HE can see that the plans and what he built are not the same ask him what and how will he make it so.Then you will still have to supervise to see that it is done correctly.
It may very well be that nothing you tell him will make him understand that what he has built now will never be right.
In my years of experience I have found out that what ppl tell you they can do as far as something you need made or fixed can be totally different than what they do.Makes me nuts.
Here's a true example:I designed a walk in animal enclosure over 30 years ago.I had everything about it perfect for my needs.When I left my husband the enclosure stayed with him.Later I had a friend build me another one.It was perfect too.Now,here comes the good part...I needed another one built and asked another friend to build it.He asked how did I want it built?I looked across the room and I said "Just like that one".
He asked me many more times how did I want it built and I kept telling him just like the one that was 15 ft.away.I told everything must be the same.All I know is when I came home from work that was the worst mess.I couldn't believe it as one was already there exactly like I wanted the new one to be.The door openings were too narrow,the shelves were all wrong I couldn't use it and he finally redid it.
Maybe it was too simple for him as he was a master carpenter and had built many multi million dollar homes.I don't know.
I wish ppl wouldn't tell me they can do something when they can't.
I hope you can get it worked out.Good luck.