I flew YYC-LHR on March 24. I saw that 19A was occupied but 19B and C were empty. On EF's seatmap, 19B was blocked but 19C was vacant. Another pax (SE judging from bag tags) scooped into 19C after takeoff. But 19A told the scooper that she had paid extra for all 3 seats. Scooper talked to the FA and FA sent the scooper back to get original seat. (During the night, 19A slept across 19A,B,C)
What happened? Can't imagine buying a J seat would be more expensive than what 19A did.