He might have not looked in the connection hoses, and/or he just thinks shooting carb cleaner at a carb with the bowl off is cleaning the jets. You have to take everything apart and inspect it all.
I have no idea how they go down the freeway...I did the same thing you are thinking of doing about a month ago, bought an old low mileage XT..... but your bike is in better condition than mine was. My bike had an original 7200km's on it (4500 miles).....
It's going back together now and looking good. If everything goes well It should be on the road in 2-3 weeks.
If it runs well there are a lot of inexpensive ways to upgrade the forks and shocks if required. Fun bike to work on.