I found this incosistency with GNU when the following command is executed: printf "a\nb\nc\nd" | csplit - 2

With GNU implementation, the csplit produces 2 files and in standard output we have:
2
5

On the other hand if I execute the same command with uutils, it produces 2 files and in standard output we have:
2
6

The difference is in the second file because uutils implementation adds automatically a \n the d letter.