I see it too on my upcoming trip. As EC was full I had not made a seat selection and see that I have now been placed there (though I am waiting for the curtain to move at T-72 hours).
If this means that they will start to fill the plane back to front (and more chance of a free seat), I’ll be quite happy (in case no EC is available).
It seems that the “product” has not yet been officially launched, no news yet on the KLM seating page:
https://www.klm.com/travel/nl_en/pre...oard/index.htm