I have an old poster of Auc Coucett. It includes drawings of him on various unicycle related contraptions. There is a drawing of him balancing on the axle of a wheelbarrow on the poster. Here is a link to a thread with pictures of the poster: Old Poster
And surely, Auc Coucett was probably not the first person to do that on a wheelbarrow. Because the professional entertainers of his time were so proprietary, it’s hard to tell who did something first. Also, several people may have “invented” the same thing independently.
Meanwhile, there were performers who claimed to have “invented” the unicycle well into the early 1900s. In other words, don’t believe anybody’s marketing materials.
From the poster, the guy seems adept at variious wheely things with attached handles, and that’s pretty much what he’s doing with the wheelbarrow i.e. kind of equivalent to a bc wheel with handles attached.