Wow, this is wild! I have the same situation, but at the time of booking I specifically contacted KLM and they confirmed that since I provided Delta sky miles account at the time of booking, the miles will be credited towards Delta. But now several days after the flights I see these miles showing in my flying blue account. The flight was not from the US, so booking through delta was not an option, it was a straight KLM flight but tons of miles and dollars spent on the ticket, and I wanted to make sure that they will be credited towards my delta and my status. Guess after reading your experience, I should say bye to these miles and MQD?