Well, many people seem desperate to give their books away on what Amazon humorously calls "promotions," so I don't see anything wrong with it. It can only be done once, and only for two weeks, you know, so it's not as though you're losing a bunch of possible sales.
Anyhow, it's a condition of doing business with KDP, so there's not much point losing sleep over it.
(Don't trust KDP to publish a print edition. Don't trust CreateSpace to publish an ebook.)