I cannot imagine 10% of luggage ever misconnected in AMS.  This just seems *sooooo* much higher than anywhere else.  Moreover, it would imply that KLM as the major user of the airport would have a rate of mishandle luggage at around 10%, which would have put them in an untenable business situation.   

More importantly, what matters is the mishandled rate now, not way back when: the rate for 2017 was 5.57 per thousands, and Delta now uses technology where they claim to handle 99.9% of all bags perfectly (as reported by the BBC [here][1]).  Given that AMS is a major Delta hub, and KLM is so intertwined with Delta, it is unlikely that the DL performance is much worse than announced when connecting to a KLM flight.

As an aside: I avoid CDG as much as I can.  I have always found AMS to be much more passenger friendly: clean, with a logical layout, and spacious wait areas, all things which CDG is NOT.


  [1]: https://www.bbc.com/news/business-48437262