A question on J seat availability. One day before OLCI of my flight opens, Expertflyer shows the following availability and some seats available at the seat map. A couple of hours before OLCI, availability of booking classes stays the same, but the seat map shows 10 'blocked' seats in J.





After OLCI opened, the seat map disappears from expertflyer (as usual) but still shows in my KLM app with 0 availability. Also not possible to upgrade from Y to J with miles or cash and availability at expertflyer is now 0. So it seems that somehow right at the moment of OLCI all seats that have been blocked just before OLCI are now booked. I see this happen more often, but it could be just a coincidence that at the exact moment when OLCI opens 10 Y pax decide to take an upgrade offer, but that still doesn't explain why the seats would be blocked beforehand.

Any ideas on why just before check-in opens KL would block 10 seats in biz while there seems to be availability to book, and why this availability goes to 0 right after OLCI opens? Could these be seats from staff with a DoD upgrade that clears somehow?