Last year I booked one of my daughters and 5 of her friends to travel to our Budapest flat. I reserved them O class HBO fares at £43 each way and made the booking over 10 months in advance. When it came to OLCI I was surprised to see them allocated seats together very far forward in rows 10 and 11 which were only a couple of rows back from CE and just behind the Economy seats reserved for passengers with status.
Budapest is a destination where very few passengers prepay for seats so I therefore make the assumption that seats were probably allocated according to booking date. At 10+ months in advance my daughter and friends were likely to have been among the first to book seats on that aircraft.