On the following file hierarchy:

.
├── dir1
│   ├── file
│   └── src
└── dir2
    └── src

dirdiff dir1 dir2 erroneously returns:

[Present in second dir. only]	"src"
[Present in first dir. only]	"src"
[Present in first dir. only]	"file"

due to inconsistencies in file ordering (that only sometimes depends on the path being a directory or not).