I was examining the seatmap for a potential flight on Finnair flight AY131 from Helsinki to Singapore, and spotted something quite odd. Per Flightradar24, this route always operates with the pride of Finnair's fleet, the Airbus A350-900. However, on some days in April, the following seatmap pops up:
This matches neither of Seatguru's two layouts for Finnair's A350-900 for Finnair's 359s: note how the middle section of the front seats is excluded from "Economy Comfort" section (starred seats), and how the last seat number is 66, not 56. This last tidbit is particularly odd, since Finnair's only other twin aisle jet (A330) maxes out at 57 rows.
What is this aircraft? Is Finnair temporarily chartering somebody else's plane, or is this a revamped A359 which already has Finnair's upcoming Premium Economy offering, which is scheduled to launch officially on May 11th?