What has surprised me was when the first SUP entered the Adirondack 90 miler a few years ago. He was absolutely last to cross the finish line on the final third day, but he got a rousing applause (in part because finally now the awards ceremony could begin). Since then there have been more entries, with slightly better time results.
Then even more unbelievable, SUPS were allowed to enter the Yukon 1000 mile race. The Y1K is totally unsupported externally and all racers must carry all food and gear they need with them for the entire time of the trip, which is normally up to 2 weeks for slower boats. Although, like any other solo paddler, they must travel in pairs for safety. I know there have been days (even more than one day), when they have been weather bound due to high winds as canoes and sea kayaks easily paddled past them.