Are you claiming a bug? Or just a point out something that caught you off guard?
The results of the VI are accurate.
In the top you used a Not a Path constant, checked it for "not a path" and the result is true.
In the top you used the same constant, and converted it to a string. The string is empty. Converted it back to a path. Now you do have a path, it just happens to be an empty path, so when you evaluate it for Not a Path, the result is false.
An empty path and a Not a Path are two different things. But you lose that information when you convert it to a string datatype.
