I'm flying HEL to LHR in June. The plane is a Finnair Airbus A350-900.

The Finnair seat selector shows the first row in economy (21) has only two seats (21A & 21C/21J & 21L) on the left and right hand seating, showing the middle seat missing (B & K). All rows behind the full have 3 seats. On seat guru (and a youtube clip I found) the floor plans show this differently with the isle seat missing (A&B/K&L).

Can anyone suggest which might be correct?