I'm flying SEA-AMS-LYS-BIQ later this month, TATL leg on DL, two subsequent legs on KLM, but AF metal. I need aisle seats (medical issue, benign by annoying). DL, KLM, and AF all tell me the same thing, that NO advance seat assignments will be made, even for Sky Team Elite Plus members. AF told me that the first time I can get those seats is at SEA when I check in for departure.

The SkyTeam site claims the benefit:

Preferred Seating: There’s a seat with your name on it. Based on availability, SkyTeam representatives make every effort to accommodate your seating preference. As a SkyTeam Elite or Elite Plus passenger, you can reserve one of a number of select seats at time of booking.

Is this a lie in general? Or does AF simply make nothing "available"? Are all the AF direct purchasers getting my seats in advance, so there will be no aisles left on the day of departure? Or will AF give me preference when they finally get around to letting me claim an actual seat?