I recently ran into this for a family member with a combined Euro/Airmiles (the Dutch version) ticket. The website says that they will only allow seat assignments on 'special' fare tickets 30 hours in advance. Basically only at check-in. You can pick your own seat on the KLM site for higher fare classes but it seems that this is now the 'enhanced' reality for award other super discount travel. One more reason to stick with NW metal.