The statement below is false.
The statement above is correct.
There's a rules foundation for this reading, too. It really is not 100% clear in the rulebook I believe, which was why I asked a rules question about this to the FFG guys back in February, and they confirmed our suspicions. The answer I got was thusly:
Question: Two enemy figures, one with 1 defense, one with 2 defense, 2 hits to assign. Am I allowed to assign one hit to the figure with 1 defense, leaving one hit to be assigned to the figure with 2 defense (and do not much good)?
Answer: Yes. In this situation, since you can fulfill the rule requiring you to assign enough hits to kill the Defense 1 unit, you are left with only 1 hit remaining, which is not sufficient to defeat the Defense 2