I'm flying LHR-AMS-JFK on a WBC award flight next month, called KLM a couple of weeks ago to select my seats. All the seats I wanted were available apparently, and have now been added to my booking.

How reliable is this service? When I go to OLCI the day before the flight, will I be offered exactly those seats? It's not a huge deal, but as we're flying out on a 777 I don't want to be saddled in the row of 3....

Do KLM also reserve the best seats for Plats at OLCI, in case I have to select seats again from scratch?