Certainly an interesting one, Easyjet clearly had no intention of having a passenger use these seats and they planned to move anyone who had booked into these seats to alternatives once all had boarded.
It appears the whole row has missing backs - which begs the more interesting question in my head, those behind had no seat pockets, tray tables, and it would make a 'brace' slightly different. Would there be sharp parts sticking out of those broken seats? who knows.