I think he has a good shot at it. That being said, yes he should be worried. Everybody should be worried. There are no guarantees for anybody. Look at some of the other recent posts where people from top med schools, great letters, 260s on the boards and research "fall through the cracks" and don't match. Based purely on a board score of 236 and data from the 2009 match he has about an 80-85% chance of matching. Those are great odds. I would put money down on that every time. But, it doesn't matter what the odds are if you end up getting the the sh*t end of the stick.
Some of the re-applicants have posted a lot about this and I remember a post about someone going unmatched twice in a row. Sadly, there are others from this year that did not match also. I'm sure a lot of them were excellent candidates as well and didn't think they had to be too worried either.
I was a very strong applicant, but after hearing stories from friends I'm just really glad to get a spot. I don't think I fully appreciated just how competitive this field really is until match day.
The stats show that a significant percentage of american graduating seniors don't match. The odds are probably in his and your favor that you will match. In fact, people match every year with much lower board scores. For the record I think mid 230s is great and he should be congratulated on doing well.
In the end, all it takes is one program to like you and you're in. But if I learned one thing this year its that it doesn't matter how baller you think your application is, you have to apply broadly and seriously consider if you would rather go unmatched than spend 5 years at a program that you are not that excited about.
Good luck