Yeah. You really need this caveat to avoid the loophole where you can compress anything to zero bytes by making the desired output a literal in your decompress

Yeah. You really need this caveat to avoid the loophole where you can compress anything to zero bytes by making the desired output a literal in your decompressor (which just ignores its input and prints the hard-coded literal). This could be considered a real-world application of "hello world" programs: Winning compression prize contests by blatantly abusing the rules.